diff --git a/core/lib/Drupal/Core/Form/EventSubscriber/FormAjaxSubscriber.php b/core/lib/Drupal/Core/Form/EventSubscriber/FormAjaxSubscriber.php
index 6c9c178..cae4398 100644
--- a/core/lib/Drupal/Core/Form/EventSubscriber/FormAjaxSubscriber.php
+++ b/core/lib/Drupal/Core/Form/EventSubscriber/FormAjaxSubscriber.php
@@ -3,7 +3,7 @@
 namespace Drupal\Core\Form\EventSubscriber;
 
 use Drupal\Core\Ajax\AjaxResponse;
-use Drupal\Core\Ajax\PrependCommand;
+use Drupal\Core\Ajax\ReplaceCommand;
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
 use Drupal\Core\Form\Exception\BrokenPostRequestException;
 use Drupal\Core\Form\FormAjaxException;
@@ -78,7 +78,7 @@ public function onException(GetResponseForExceptionEvent $event) {
       $this->drupalSetMessage($this->t('An unrecoverable error occurred. The uploaded file likely exceeded the maximum file size (@size) that this server supports.', ['@size' => $this->formatSize($exception->getSize())]), 'error');
       $response = new AjaxResponse();
       $status_messages = ['#type' => 'status_messages'];
-      $response->addCommand(new PrependCommand(NULL, $status_messages));
+      $response->addCommand(new ReplaceCommand(NULL, $status_messages));
       $response->headers->set('X-Status-Code', 200);
       $event->setResponse($response);
       return;
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index bb203bf..b9d84e4 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -661,11 +661,17 @@ function template_preprocess_comment(&$variables) {
   else {
     $uri = $comment->permalink();
     $attributes = $uri->getOption('attributes') ?: [];
-    $attributes += ['class' => ['permalink'], 'rel' => 'bookmark'];
+    $attributes += ['class' => ['permalink']];
+    if (CommentType::load($comment->bundle())->getNofollow()) {
+      $attributes += ['rel' => 'bookmark nofollow'];
+    }
+    else {
+      $attributes += ['rel' => 'bookmark'];
+    }
     $uri->setOption('attributes', $attributes);
     $variables['title'] = \Drupal::l($comment->getSubject(), $uri);
 
-    $variables['permalink'] = \Drupal::l(t('Permalink'), $comment->permalink());
+    $variables['permalink'] = \Drupal::l(t('Permalink'), $uri);
   }
 
   $variables['submitted'] = t('Submitted by @username on @datetime', ['@username' => $variables['author'], '@datetime' => $variables['created']]);
@@ -690,7 +696,13 @@ function template_preprocess_comment(&$variables) {
     }
     $permalink_uri_parent = $comment_parent->permalink();
     $attributes = $permalink_uri_parent->getOption('attributes') ?: [];
-    $attributes += ['class' => ['permalink'], 'rel' => 'bookmark'];
+    $attributes += ['class' => ['permalink']];
+    if (CommentType::load($comment_parent->bundle())->getNofollow()) {
+      $attributes += ['rel' => 'bookmark nofollow'];
+    }
+    else {
+      $attributes += ['rel' => 'bookmark'];
+    }
     $permalink_uri_parent->setOption('attributes', $attributes);
     $variables['parent_title'] = \Drupal::l($comment_parent->getSubject(), $permalink_uri_parent);
     $variables['parent_permalink'] = \Drupal::l(t('Parent permalink'), $permalink_uri_parent);
diff --git a/core/modules/comment/config/schema/comment.schema.yml b/core/modules/comment/config/schema/comment.schema.yml
index e4a5b75..2ea37da 100644
--- a/core/modules/comment/config/schema/comment.schema.yml
+++ b/core/modules/comment/config/schema/comment.schema.yml
@@ -58,6 +58,9 @@ comment.type.*:
     description:
       type: text
       label: 'Description'
+    nofollow:
+      type: boolean
+      label: 'Rel nofollow'
 
 field.storage_settings.comment:
   type: mapping
diff --git a/core/modules/comment/src/CommentTypeForm.php b/core/modules/comment/src/CommentTypeForm.php
index 0ac5b44..64033b7 100644
--- a/core/modules/comment/src/CommentTypeForm.php
+++ b/core/modules/comment/src/CommentTypeForm.php
@@ -122,6 +122,13 @@ public function form(array $form, FormStateInterface $form_state) {
       ];
     }
 
+    $form['nofollow'] = [
+      '#type' => 'checkbox',
+      '#title' => t('Nofollow'),
+      '#default_value' => $comment_type->getNofollow(),
+      '#description' => t('Add nofollow to rel attribute of comment type.'),
+    ];
+
     if ($this->moduleHandler->moduleExists('content_translation')) {
       $form['language'] = [
         '#type' => 'details',
diff --git a/core/modules/comment/src/CommentTypeInterface.php b/core/modules/comment/src/CommentTypeInterface.php
index acde96c..a82bab3 100644
--- a/core/modules/comment/src/CommentTypeInterface.php
+++ b/core/modules/comment/src/CommentTypeInterface.php
@@ -35,4 +35,12 @@ public function setDescription($description);
    */
   public function getTargetEntityTypeId();
 
+  /**
+   * Gets the setting of rel's nofollow for this comment type.
+   *
+   * @return bool
+   *   TRUE if the comment type has the rel set to nofollow, FALSE otherwise.
+   */
+  public function getNofollow();
+
 }
diff --git a/core/modules/comment/src/Entity/CommentType.php b/core/modules/comment/src/Entity/CommentType.php
index a773c58..62009db 100644
--- a/core/modules/comment/src/Entity/CommentType.php
+++ b/core/modules/comment/src/Entity/CommentType.php
@@ -44,6 +44,7 @@
  *     "label",
  *     "target_entity_type_id",
  *     "description",
+ *     "nofollow",
  *   }
  * )
  */
@@ -78,6 +79,13 @@ class CommentType extends ConfigEntityBundleBase implements CommentTypeInterface
   protected $target_entity_type_id;
 
   /**
+   * Whether the comment type has rel set to nofollow.
+   *
+   * @var bool
+   */
+  protected $nofollow = TRUE;
+
+  /**
    * {@inheritdoc}
    */
   public function getDescription() {
@@ -99,4 +107,11 @@ public function getTargetEntityTypeId() {
     return $this->target_entity_type_id;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getNofollow() {
+    return $this->nofollow;
+  }
+
 }
diff --git a/core/modules/comment/src/Tests/CommentTestBase.php b/core/modules/comment/src/Tests/CommentTestBase.php
index 3b923ff..7210065 100644
--- a/core/modules/comment/src/Tests/CommentTestBase.php
+++ b/core/modules/comment/src/Tests/CommentTestBase.php
@@ -401,6 +401,7 @@ protected function createCommentType($label) {
       'label' => $label,
       'description' => '',
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
     ]);
     $bundle->save();
     return $bundle;
diff --git a/core/modules/comment/src/Tests/CommentTestTrait.php b/core/modules/comment/src/Tests/CommentTestTrait.php
index 038a3df..739aace 100644
--- a/core/modules/comment/src/Tests/CommentTestTrait.php
+++ b/core/modules/comment/src/Tests/CommentTestTrait.php
@@ -47,6 +47,7 @@ public function addDefaultCommentField($entity_type, $bundle, $field_name = 'com
         'id' => $comment_type_id,
         'label' => Unicode::ucfirst($comment_type_id),
         'target_entity_type_id' => $entity_type,
+        'nofollow' => TRUE,
         'description' => 'Default comment field',
       ])->save();
     }
diff --git a/core/modules/comment/tests/src/Functional/CommentFieldsTest.php b/core/modules/comment/tests/src/Functional/CommentFieldsTest.php
index 2df9973..dc5aa2f 100644
--- a/core/modules/comment/tests/src/Functional/CommentFieldsTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentFieldsTest.php
@@ -168,6 +168,7 @@ public function testCommentFieldCreate() {
       'label' => 'user_comment_type',
       'description' => '',
       'target_entity_type_id' => 'user',
+      'nofollow' => TRUE,
     ]);
     $bundle->save();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php b/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
index 7342633..e3293dd 100644
--- a/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
@@ -80,10 +80,11 @@ public function testCommentInterface() {
     $this->assertText($comment_text, 'Individual comment body found.');
     $arguments = [
       ':link' => base_path() . 'comment/' . $comment->id() . '#comment-' . $comment->id(),
+      ':rel' => 'nofollow',
     ];
-    $pattern_permalink = '//footer[contains(@class,"comment__meta")]/a[contains(@href,:link) and text()="Permalink"]';
+    $pattern_permalink = '//footer[contains(@class,"comment__meta")]/a[contains(@href,:link) and contains(@rel,:rel) and text()="Permalink"]';
     $permalink = $this->xpath($pattern_permalink, $arguments);
-    $this->assertTrue(!empty($permalink), 'Permalink link found.');
+    $this->assertTrue(!empty($permalink), 'Permalink link found and rel is set to nofollow.');
 
     // Set comments to have subject and preview to optional.
     $this->drupalLogout();
diff --git a/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php b/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
index 5889d69..19dc593 100644
--- a/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
@@ -56,6 +56,7 @@ protected function setUp() {
       'label' => 'Comment settings',
       'description' => 'Comment settings',
       'target_entity_type_id' => 'entity_test',
+      'nofollow' => TRUE,
     ])->save();
     // Create comment field on entity_test bundle.
     $this->addDefaultCommentField('entity_test', 'entity_test');
@@ -411,6 +412,7 @@ public function testCommentFunctionality() {
       'label' => 'Foobar',
       'description' => '',
       'target_entity_type_id' => 'entity_test',
+      'nofollow' => TRUE,
     ]);
     $bundle->save();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentTestBase.php b/core/modules/comment/tests/src/Functional/CommentTestBase.php
index 7cadcbf..e00126c 100644
--- a/core/modules/comment/tests/src/Functional/CommentTestBase.php
+++ b/core/modules/comment/tests/src/Functional/CommentTestBase.php
@@ -395,6 +395,7 @@ protected function createCommentType($label) {
       'label' => $label,
       'description' => '',
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
     ]);
     $bundle->save();
     return $bundle;
diff --git a/core/modules/comment/tests/src/Functional/CommentTitleTest.php b/core/modules/comment/tests/src/Functional/CommentTitleTest.php
index 65c4937..b6b5967 100644
--- a/core/modules/comment/tests/src/Functional/CommentTitleTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentTitleTest.php
@@ -77,6 +77,11 @@ public function testCommentPopulatedTitles() {
     // Tests that the comment's title link contains the url fragment.
     $this->assertTrue(strpos($comment_permalink, '#comment-' . $comment1->id()), "The comment's title link contains the url fragment.");
     $this->assertEqual($comment1->permalink()->toString(), $comment_permalink, "The comment's title has the correct link.");
+
+    $comment_permalink_rel = $this->cssSelect('.permalink');
+    $comment_permalink_rel = $comment_permalink_rel[0]->getAttribute('rel');
+    // Tests that the comment's title link contains the nofollow rel.
+    $this->assertTrue(strpos($comment_permalink_rel, 'nofollow'), "The comment's title link contains the nofollow rel.");
   }
 
 }
diff --git a/core/modules/comment/tests/src/Functional/CommentTypeNofollowTest.php b/core/modules/comment/tests/src/Functional/CommentTypeNofollowTest.php
new file mode 100644
index 0000000..0f79376
--- /dev/null
+++ b/core/modules/comment/tests/src/Functional/CommentTypeNofollowTest.php
@@ -0,0 +1,151 @@
+<?php
+
+namespace Drupal\Tests\comment\Functional;
+
+use Drupal\comment\Entity\Comment;
+use Drupal\comment\Entity\CommentType;
+use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
+use Drupal\node\Entity\Node;
+
+/**
+ * Ensures that comment type implemented nofollow functionality work correctly.
+ *
+ * @group comment
+ */
+class CommentTypeNofollowTest extends CommentTestBase {
+
+  /**
+   * Admin user.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $adminUser;
+
+  /**
+   * Admin user.
+   *
+   * @var \Drupal\comment\Entity\CommentType
+   */
+  protected $commentType;
+
+  /**
+   * Permissions to grant admin user.
+   *
+   * @var array
+   */
+  protected $permissions = [
+    'administer comments',
+    'administer comment fields',
+    'administer comment types',
+  ];
+
+  /**
+   * Sets the test up.
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->adminUser = $this->drupalCreateUser($this->permissions);
+
+    $this->commentType = $this->createCommentType('other');
+
+  }
+
+  /**
+   * Tests editing a comment type defined nofollow.
+   */
+  public function testCommentTypeEditNofollow() {
+    // Log in a test user.
+    $this->drupalLogin($this->adminUser);
+
+    $this->drupalGet('admin/structure/comment/manage/' . $this->commentType->id());
+    $this->assertResponse(200, 'The comment type can be accessed at the edit form.');
+
+    // Edit the nofollow setting via the user interface.
+    $edit = [
+      'nofollow' => FALSE,
+    ];
+    $this->drupalPostForm('admin/structure/comment/manage/' . $this->commentType->id(), $edit, t('Save'));
+    \Drupal::entityManager()->getStorage('comment_type')->resetCache(['other']);
+    $comment_type = CommentType::load('other');
+    $this->assertEqual($comment_type->getNofollow(), FALSE);
+  }
+
+  public function testCommentViewCommentTypeNofollow() {
+    // Log in a test user.
+    $this->drupalLogin($this->adminUser);
+
+    $this->drupalCreateContentType(['type' => 'test_node']);
+    $this->addDefaultCommentField('node', 'test_node', 'comment_other', CommentItemInterface::OPEN, 'other');
+
+    $this->drupalGet('admin/structure/comment/manage/' . $this->commentType->id());
+    $this->assertResponse(200, 'The comment type can be accessed at the edit form.');
+
+    // Change the nofollow to FALSE.
+    $edit = [
+      'nofollow' => FALSE,
+    ];
+    $this->drupalPostForm('admin/structure/comment/manage/' . $this->commentType->id(), $edit, t('Save'));
+    \Drupal::entityManager()->getStorage('comment_type')->resetCache(['other']);
+    $this->commentType = CommentType::load('other');
+
+    // Create a comment.
+    $comment = Comment::create([
+      'subject' => $this->randomMachineName(8),
+      'comment_body' => $this->randomMachineName(8),
+      'entity_id' => 'test_node',
+      'entity_type' => 'node',
+      'field_name' => 'comment_other',
+      'status' => CommentInterface::PUBLISHED,
+    ]);
+    $comment->save();
+
+    // Check the nofollow on the comment page.
+    $this->drupalGet('comment/' . $comment->id());
+    $arguments = [
+      ':rel' => 'nofollow',
+    ];
+    $pattern_permalink = '//footer[contains(@class,"comment__meta")]/a[contains(@rel,:rel) and text()="Permalink"]';
+    $permalink = $this->xpath($pattern_permalink, $arguments);
+    $this->assertFalse(!empty($permalink), 'Permalink link found and rel is not set to nofollow.');
+
+    // Check the nofollow on the reply page.
+    $this->drupalGet('comment/reply/node/' . $this->node->id() . '/comment_other/' . $comment->id());
+    $arguments = [
+      ':rel' => 'nofollow',
+    ];
+    $pattern_permalink = '//footer[contains(@class,"comment__meta")]/a[contains(@rel,:rel) and text()="Permalink"]';
+    $permalink = $this->xpath($pattern_permalink, $arguments);
+    $this->assertFalse(!empty($permalink), 'Permalink link found and rel is not set to nofollow.');
+
+    $this->drupalGet('admin/structure/comment/manage/' . $this->commentType->id());
+    $this->assertResponse(200, 'The comment type can be accessed at the edit form.');
+
+    // Change the nofollow back to its default value: TRUE.
+    $edit = [
+      'nofollow' => TRUE,
+    ];
+    $this->drupalPostForm('admin/structure/comment/manage/' . $this->commentType->id(), $edit, t('Save'));
+    \Drupal::entityManager()->getStorage('comment_type')->resetCache(['other']);
+    $this->commentType = CommentType::load('other');
+
+    // Check the nofollow on the comment page.
+    $this->drupalGet('comment/' . $comment->id());
+    $arguments = [
+      ':rel' => 'nofollow',
+    ];
+    $pattern_permalink = '//footer[contains(@class,"comment__meta")]/a[contains(@rel,:rel) and text()="Permalink"]';
+    $permalink = $this->xpath($pattern_permalink, $arguments);
+    $this->assertTrue(!empty($permalink), 'Permalink link found and rel is set to nofollow.');
+
+    // Check the nofollow on the reply page.
+    $this->drupalGet('comment/reply/node/' . $this->node->id() . '/comment_other/' . $comment->id());
+    $arguments = [
+      ':rel' => 'nofollow',
+    ];
+    $pattern_permalink = '//footer[contains(@class,"comment__meta")]/a[contains(@rel,:rel) and text()="Permalink"]';
+    $permalink = $this->xpath($pattern_permalink, $arguments);
+    $this->assertTrue(!empty($permalink), 'Permalink link found and rel is set to nofollow.');
+  }
+
+}
diff --git a/core/modules/comment/tests/src/Functional/CommentTypeTest.php b/core/modules/comment/tests/src/Functional/CommentTypeTest.php
index 291f9dc..b84f071 100644
--- a/core/modules/comment/tests/src/Functional/CommentTypeTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentTypeTest.php
@@ -67,6 +67,7 @@ public function testCommentTypeCreation() {
       'label' => 'title for foo',
       'description' => '',
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
     ];
     $this->drupalPostForm('admin/structure/comment/types/add', $edit, t('Save'));
     $comment_type = CommentType::load('foo');
diff --git a/core/modules/comment/tests/src/Kernel/CommentBundlesTest.php b/core/modules/comment/tests/src/Kernel/CommentBundlesTest.php
index d907233..de1c84a 100644
--- a/core/modules/comment/tests/src/Kernel/CommentBundlesTest.php
+++ b/core/modules/comment/tests/src/Kernel/CommentBundlesTest.php
@@ -51,6 +51,7 @@ protected function setUp() {
         'id' => 'comment_on_' . $id,
         'label' => 'Comment on ' . $label,
         'target_entity_type_id' => $id,
+        'nofollow' => TRUE,
       ])->save();
     }
   }
diff --git a/core/modules/comment/tests/src/Kernel/CommentFieldAccessTest.php b/core/modules/comment/tests/src/Kernel/CommentFieldAccessTest.php
index 1e0fd72..0d7c377 100644
--- a/core/modules/comment/tests/src/Kernel/CommentFieldAccessTest.php
+++ b/core/modules/comment/tests/src/Kernel/CommentFieldAccessTest.php
@@ -99,6 +99,7 @@ public function testAccessToAdministrativeFields() {
       'label' => 'Default comments',
       'description' => 'Default comment field',
       'target_entity_type_id' => 'entity_test',
+      'nofollow' => TRUE,
     ]);
     $comment_type->save();
 
diff --git a/core/modules/comment/tests/src/Kernel/CommentIntegrationTest.php b/core/modules/comment/tests/src/Kernel/CommentIntegrationTest.php
index af73034..8db24e4 100644
--- a/core/modules/comment/tests/src/Kernel/CommentIntegrationTest.php
+++ b/core/modules/comment/tests/src/Kernel/CommentIntegrationTest.php
@@ -37,6 +37,7 @@ protected function setUp() {
     CommentType::create([
       'id' => 'comment',
       'label' => $this->randomString(),
+      'nofollow' => TRUE,
     ])->save();
   }
 
diff --git a/core/modules/comment/tests/src/Kernel/CommentStringIdEntitiesTest.php b/core/modules/comment/tests/src/Kernel/CommentStringIdEntitiesTest.php
index adbe1b0..2f6519c 100644
--- a/core/modules/comment/tests/src/Kernel/CommentStringIdEntitiesTest.php
+++ b/core/modules/comment/tests/src/Kernel/CommentStringIdEntitiesTest.php
@@ -45,6 +45,7 @@ public function testCommentFieldNonStringId() {
         'label' => 'foo',
         'description' => '',
         'target_entity_type_id' => 'entity_test_string_id',
+        'nofollow' => TRUE,
       ]);
       $bundle->save();
       $field_storage = FieldStorageConfig::create([
diff --git a/core/modules/comment/tests/src/Kernel/CommentValidationTest.php b/core/modules/comment/tests/src/Kernel/CommentValidationTest.php
index 98b7715..fe6eae6 100644
--- a/core/modules/comment/tests/src/Kernel/CommentValidationTest.php
+++ b/core/modules/comment/tests/src/Kernel/CommentValidationTest.php
@@ -42,6 +42,7 @@ public function testValidation() {
       'id' => 'comment',
       'label' => 'comment',
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
     ])->save();
 
     // Add comment field to content.
diff --git a/core/modules/comment/tests/src/Kernel/Migrate/MigrateCommentStubTest.php b/core/modules/comment/tests/src/Kernel/Migrate/MigrateCommentStubTest.php
index 0b256ea..cf3744f 100644
--- a/core/modules/comment/tests/src/Kernel/Migrate/MigrateCommentStubTest.php
+++ b/core/modules/comment/tests/src/Kernel/Migrate/MigrateCommentStubTest.php
@@ -48,6 +48,7 @@ protected function setUp() {
       'id' => 'testcommenttype',
       'label' => 'Test comment type',
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
     ])->save();
   }
 
diff --git a/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php b/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php
index 86e8949..f9c553d 100644
--- a/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php
+++ b/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php
@@ -87,6 +87,7 @@ protected function setUp($import_test_views = TRUE) {
       'label' => 'Default comments',
       'target_entity_type_id' => 'entity_test',
       'description' => 'Default comment field',
+      'nofollow' => TRUE,
     ])->save();
     // Create a commented entity.
     $entity = EntityTest::create();
diff --git a/core/modules/field/tests/src/Kernel/Migrate/d7/MigrateFieldFormatterSettingsTest.php b/core/modules/field/tests/src/Kernel/Migrate/d7/MigrateFieldFormatterSettingsTest.php
index 576e86a..e4ea59a 100644
--- a/core/modules/field/tests/src/Kernel/Migrate/d7/MigrateFieldFormatterSettingsTest.php
+++ b/core/modules/field/tests/src/Kernel/Migrate/d7/MigrateFieldFormatterSettingsTest.php
@@ -42,26 +42,32 @@ protected function setUp() {
     CommentType::create([
       'id' => 'comment_node_page',
       'label' => $this->randomMachineName(),
+      'nofollow' => TRUE,
     ])->save();
     CommentType::create([
       'id' => 'comment_node_article',
       'label' => $this->randomMachineName(),
+      'nofollow' => TRUE,
     ])->save();
     CommentType::create([
       'id' => 'comment_node_blog',
       'label' => $this->randomMachineName(),
+      'nofollow' => TRUE,
     ])->save();
     CommentType::create([
       'id' => 'comment_node_book',
       'label' => $this->randomMachineName(),
+      'nofollow' => TRUE,
     ])->save();
     CommentType::create([
       'id' => 'comment_forum',
       'label' => $this->randomMachineName(),
+      'nofollow' => TRUE,
     ])->save();
     CommentType::create([
       'id' => 'comment_node_test_content_type',
       'label' => $this->randomMachineName(),
+      'nofollow' => TRUE,
     ])->save();
 
     NodeType::create([
diff --git a/core/modules/file/tests/src/Functional/FileFieldCreationTrait.php b/core/modules/file/tests/src/Functional/FileFieldCreationTrait.php
deleted file mode 100644
index 89c713e..0000000
--- a/core/modules/file/tests/src/Functional/FileFieldCreationTrait.php
+++ /dev/null
@@ -1,86 +0,0 @@
-<?php
-
-namespace Drupal\Tests\file\Functional;
-
-use Drupal\field\Entity\FieldStorageConfig;
-use Drupal\field\Entity\FieldConfig;
-
-/**
- * Provides methods for creating file fields.
- */
-trait FileFieldCreationTrait {
-
-  /**
-   * Creates a new file field.
-   *
-   * @param string $name
-   *   The name of the new field (all lowercase), exclude the "field_" prefix.
-   * @param string $entity_type
-   *   The entity type.
-   * @param string $bundle
-   *   The bundle that this field will be added to.
-   * @param array $storage_settings
-   *   A list of field storage settings that will be added to the defaults.
-   * @param array $field_settings
-   *   A list of instance settings that will be added to the instance defaults.
-   * @param array $widget_settings
-   *   A list of widget settings that will be added to the widget defaults.
-   *
-   * @return \Drupal\field\FieldStorageConfigInterface
-   *   The file field.
-   */
-  public function createFileField($name, $entity_type, $bundle, $storage_settings = [], $field_settings = [], $widget_settings = []) {
-    $field_storage = FieldStorageConfig::create([
-      'entity_type' => $entity_type,
-      'field_name' => $name,
-      'type' => 'file',
-      'settings' => $storage_settings,
-      'cardinality' => !empty($storage_settings['cardinality']) ? $storage_settings['cardinality'] : 1,
-    ]);
-    $field_storage->save();
-
-    $this->attachFileField($name, $entity_type, $bundle, $field_settings, $widget_settings);
-    return $field_storage;
-  }
-
-  /**
-   * Attaches a file field to an entity.
-   *
-   * @param string $name
-   *   The name of the new field (all lowercase), exclude the "field_" prefix.
-   * @param string $entity_type
-   *   The entity type this field will be added to.
-   * @param string $bundle
-   *   The bundle this field will be added to.
-   * @param array $field_settings
-   *   A list of field settings that will be added to the defaults.
-   * @param array $widget_settings
-   *   A list of widget settings that will be added to the widget defaults.
-   */
-  public function attachFileField($name, $entity_type, $bundle, $field_settings = [], $widget_settings = []) {
-    $field = [
-      'field_name' => $name,
-      'label' => $name,
-      'entity_type' => $entity_type,
-      'bundle' => $bundle,
-      'required' => !empty($field_settings['required']),
-      'settings' => $field_settings,
-    ];
-    FieldConfig::create($field)->save();
-
-    entity_get_form_display($entity_type, $bundle, 'default')
-      ->setComponent($name, [
-        'type' => 'file_generic',
-        'settings' => $widget_settings,
-      ])
-      ->save();
-    // Assign display settings.
-    entity_get_display($entity_type, $bundle, 'default')
-      ->setComponent($name, [
-        'label' => 'hidden',
-        'type' => 'file_default',
-      ])
-      ->save();
-  }
-
-}
diff --git a/core/modules/file/tests/src/Functional/FileFieldTestBase.php b/core/modules/file/tests/src/Functional/FileFieldTestBase.php
index f3d1c22..937bf21 100644
--- a/core/modules/file/tests/src/Functional/FileFieldTestBase.php
+++ b/core/modules/file/tests/src/Functional/FileFieldTestBase.php
@@ -13,8 +13,6 @@
  */
 abstract class FileFieldTestBase extends BrowserTestBase {
 
-  use FileFieldCreationTrait;
-
   /**
   * Modules to enable.
   *
@@ -60,6 +58,76 @@ public function getLastFileId() {
   }
 
   /**
+   * Creates a new file field.
+   *
+   * @param string $name
+   *   The name of the new field (all lowercase), exclude the "field_" prefix.
+   * @param string $entity_type
+   *   The entity type.
+   * @param string $bundle
+   *   The bundle that this field will be added to.
+   * @param array $storage_settings
+   *   A list of field storage settings that will be added to the defaults.
+   * @param array $field_settings
+   *   A list of instance settings that will be added to the instance defaults.
+   * @param array $widget_settings
+   *   A list of widget settings that will be added to the widget defaults.
+   */
+  public function createFileField($name, $entity_type, $bundle, $storage_settings = [], $field_settings = [], $widget_settings = []) {
+    $field_storage = FieldStorageConfig::create([
+      'entity_type' => $entity_type,
+      'field_name' => $name,
+      'type' => 'file',
+      'settings' => $storage_settings,
+      'cardinality' => !empty($storage_settings['cardinality']) ? $storage_settings['cardinality'] : 1,
+    ]);
+    $field_storage->save();
+
+    $this->attachFileField($name, $entity_type, $bundle, $field_settings, $widget_settings);
+    return $field_storage;
+  }
+
+  /**
+   * Attaches a file field to an entity.
+   *
+   * @param string $name
+   *   The name of the new field (all lowercase), exclude the "field_" prefix.
+   * @param string $entity_type
+   *   The entity type this field will be added to.
+   * @param string $bundle
+   *   The bundle this field will be added to.
+   * @param array $field_settings
+   *   A list of field settings that will be added to the defaults.
+   * @param array $widget_settings
+   *   A list of widget settings that will be added to the widget defaults.
+   */
+  public function attachFileField($name, $entity_type, $bundle, $field_settings = [], $widget_settings = []) {
+    $field = [
+      'field_name' => $name,
+      'label' => $name,
+      'entity_type' => $entity_type,
+      'bundle' => $bundle,
+      'required' => !empty($field_settings['required']),
+      'settings' => $field_settings,
+    ];
+    FieldConfig::create($field)->save();
+
+    entity_get_form_display($entity_type, $bundle, 'default')
+      ->setComponent($name, [
+        'type' => 'file_generic',
+        'settings' => $widget_settings,
+      ])
+      ->save();
+    // Assign display settings.
+    entity_get_display($entity_type, $bundle, 'default')
+      ->setComponent($name, [
+        'label' => 'hidden',
+        'type' => 'file_default',
+      ])
+      ->save();
+  }
+
+  /**
    * Updates an existing file field with new settings.
    */
   public function updateFileField($name, $type_name, $field_settings = [], $widget_settings = []) {
diff --git a/core/modules/file/tests/src/FunctionalJavascript/MaximumFileSizeExceededUploadTest.php b/core/modules/file/tests/src/FunctionalJavascript/MaximumFileSizeExceededUploadTest.php
deleted file mode 100644
index 7ccd2b2..0000000
--- a/core/modules/file/tests/src/FunctionalJavascript/MaximumFileSizeExceededUploadTest.php
+++ /dev/null
@@ -1,119 +0,0 @@
-<?php
-
-namespace Drupal\Tests\file\FunctionalJavascript;
-
-use Drupal\Component\Utility\Bytes;
-use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
-use Drupal\Tests\TestFileCreationTrait;
-use Drupal\Tests\file\Functional\FileFieldCreationTrait;
-
-/**
- * Tests uploading a file that exceeds the maximum file size.
- *
- * @group file
- */
-class MaximumFileSizeExceededUploadTest extends JavascriptTestBase {
-
-  use FileFieldCreationTrait;
-  use TestFileCreationTrait;
-
-  /**
-   * {@inheritdoc}
-   */
-  public static $modules = ['node', 'file'];
-
-  /**
-   * The file system service.
-   *
-   * @var \Drupal\Core\File\FileSystemInterface
-   */
-  protected $fileSystem;
-
-  /**
-   * A test user.
-   *
-   * @var \Drupal\user\UserInterface
-   */
-  protected $user;
-
-  /**
-   * The original value of the 'display_errors' PHP configuration option.
-   *
-   * @todo Remove this when issue #2905597 is fixed.
-   * @see https://www.drupal.org/node/2905597
-   *
-   * @var string
-   */
-  protected $originalDisplayErrorsValue;
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setUp() {
-    parent::setUp();
-
-    $this->fileSystem = $this->container->get('file_system');
-
-    // Create the Article node type.
-    $this->drupalCreateContentType(['type' => 'article', 'name' => 'Article']);
-
-    // Attach a file field to the node type.
-    $field_settings = ['file_extensions' => 'txt'];
-    $this->createFileField('field_file', 'node', 'article', [], $field_settings);
-
-    // Log in as a content author who can create Articles.
-    $this->user = $this->drupalCreateUser([
-      'access content',
-      'create article content',
-    ]);
-    $this->drupalLogin($this->user);
-
-    // Disable the displaying of errors, so that the AJAX responses are not
-    // contaminated with error messages about exceeding the maximum POST size.
-    // @todo Remove this when issue #2905597 is fixed.
-    // @see https://www.drupal.org/node/2905597
-    $this->originalDisplayErrorsValue = ini_set('display_errors', '0');
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function tearDown() {
-    // Restore the displaying of errors to the original value.
-    // @todo Remove this when issue #2905597 is fixed.
-    // @see https://www.drupal.org/node/2905597
-    ini_set('display_errors', $this->originalDisplayErrorsValue);
-
-    parent::tearDown();
-  }
-
-  /**
-   * Tests that uploading files exceeding maximum size are handled correctly.
-   */
-  public function testUploadFileExceedingMaximumFileSize() {
-    $session = $this->getSession();
-
-    // Create a test file that exceeds the maximum POST size with 1 kilobyte.
-    $post_max_size = Bytes::toInt(ini_get('post_max_size'));
-    $invalid_file = $this->generateFile('exceeding_post_max_size', ceil(($post_max_size + 1024) / 1024), 1024);
-
-    // Go to the node creation form and try to upload the test file.
-    $this->drupalGet('node/add/article');
-    $page = $session->getPage();
-    $page->attachFileToField("files[field_file_0]", $this->fileSystem->realpath($invalid_file));
-
-    // An error message should appear informing the user that the file exceeded
-    // the maximum file size.
-    $this->assertSession()->waitForElement('css', '.messages--error');
-    // The error message includes the actual file size limit which depends on
-    // the current environment, so we check for a part of the message.
-    $this->assertSession()->pageTextContains('An unrecoverable error occurred. The uploaded file likely exceeded the maximum file size');
-
-    // Now upload a valid file and check that the error message disappears.
-    $valid_file = $this->generateFile('not_exceeding_post_max_size', 8, 8);
-    $page->attachFileToField("files[field_file_0]", $this->fileSystem->realpath($valid_file));
-    $this->assertSession()->waitForElement('named', ['id_or_name', 'field_file_0_remove_button']);
-    $this->assertSession()->elementNotExists('css', '.messages--error');
-  }
-
-}
diff --git a/core/modules/forum/config/optional/comment.type.comment_forum.yml b/core/modules/forum/config/optional/comment.type.comment_forum.yml
index 44a2d65..825c92a 100644
--- a/core/modules/forum/config/optional/comment.type.comment_forum.yml
+++ b/core/modules/forum/config/optional/comment.type.comment_forum.yml
@@ -8,3 +8,4 @@ id: comment_forum
 label: Comment_forum
 target_entity_type_id: node
 description: 'Default comment field'
+nofollow: TRUE
diff --git a/core/modules/migrate/tests/src/Kernel/NodeCommentCombinationTrait.php b/core/modules/migrate/tests/src/Kernel/NodeCommentCombinationTrait.php
index 6f04b3a..f4b6939 100644
--- a/core/modules/migrate/tests/src/Kernel/NodeCommentCombinationTrait.php
+++ b/core/modules/migrate/tests/src/Kernel/NodeCommentCombinationTrait.php
@@ -32,6 +32,7 @@ protected function createNodeCommentCombination($node_type, $comment_type = NULL
       'id' => $comment_type,
       'label' => $this->randomString(),
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
     ])->save();
   }
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/CommentType/CommentTypeResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/CommentType/CommentTypeResourceTestBase.php
index 9d88211..968998a 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/CommentType/CommentTypeResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/CommentType/CommentTypeResourceTestBase.php
@@ -44,6 +44,7 @@ protected function createEntity() {
       'label' => 'Camelids',
       'description' => 'Camelids are large, strictly herbivorous animals with slender necks and long legs.',
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
     ]);
 
     $camelids->save();
@@ -63,6 +64,7 @@ protected function getExpectedNormalizedEntity() {
       'langcode' => 'en',
       'status' => TRUE,
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
       'uuid' => $this->entity->uuid(),
     ];
   }
diff --git a/core/modules/views/tests/src/Kernel/Entity/ViewEntityDependenciesTest.php b/core/modules/views/tests/src/Kernel/Entity/ViewEntityDependenciesTest.php
index 4929c7e..e826bca 100644
--- a/core/modules/views/tests/src/Kernel/Entity/ViewEntityDependenciesTest.php
+++ b/core/modules/views/tests/src/Kernel/Entity/ViewEntityDependenciesTest.php
@@ -47,6 +47,7 @@ protected function setUp($import_test_views = TRUE) {
       'label' => 'Comment settings',
       'description' => 'Comment settings',
       'target_entity_type_id' => 'node',
+      'nofollow' => TRUE,
     ]);
     $comment_type->save();
 
diff --git a/core/profiles/standard/config/install/comment.type.comment.yml b/core/profiles/standard/config/install/comment.type.comment.yml
index ddcbbc9..e64186f 100644
--- a/core/profiles/standard/config/install/comment.type.comment.yml
+++ b/core/profiles/standard/config/install/comment.type.comment.yml
@@ -5,3 +5,4 @@ id: comment
 label: 'Default comments'
 target_entity_type_id: node
 description: 'Allows commenting on content'
+nofollow: TRUE
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityDisplayBaseTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityDisplayBaseTest.php
index ec1a55c..1911dc1 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityDisplayBaseTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityDisplayBaseTest.php
@@ -67,6 +67,7 @@ public function testOnDependencyRemoval() {
       'label' => 'entity_test',
       'description' => '',
       'target_entity_type_id' => 'entity_test',
+      'nofollow' => TRUE,
     ]);
     $comment_bundle->save();
     $comment_display = EntityViewDisplay::create([
diff --git a/core/tests/Drupal/Tests/Core/Form/EventSubscriber/FormAjaxSubscriberTest.php b/core/tests/Drupal/Tests/Core/Form/EventSubscriber/FormAjaxSubscriberTest.php
index 278ec06..050d745 100644
--- a/core/tests/Drupal/Tests/Core/Form/EventSubscriber/FormAjaxSubscriberTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/EventSubscriber/FormAjaxSubscriberTest.php
@@ -181,7 +181,7 @@ public function testOnExceptionBrokenPostRequest() {
     $this->assertSame(200, $actual_response->headers->get('X-Status-Code'));
     $expected_commands[] = [
       'command' => 'insert',
-      'method' => 'prepend',
+      'method' => 'replaceWith',
       'selector' => NULL,
       'data' => $rendered_output,
       'settings' => NULL,
diff --git a/core/tests/Drupal/Tests/TestFileCreationTrait.php b/core/tests/Drupal/Tests/TestFileCreationTrait.php
index a2f119b..5bb5394 100644
--- a/core/tests/Drupal/Tests/TestFileCreationTrait.php
+++ b/core/tests/Drupal/Tests/TestFileCreationTrait.php
@@ -164,8 +164,7 @@ public static function generateFile($filename, $width, $lines, $type = 'binary-t
     }
 
     // Create filename.
-    $filename = 'public://' . $filename . '.txt';
-    file_put_contents($filename, $text);
+    file_put_contents('public://' . $filename . '.txt', $text);
     return $filename;
   }