diff --git a/core/modules/comment/lib/Drupal/comment/CommentFormController.php b/core/modules/comment/lib/Drupal/comment/CommentFormController.php
index e9759eb..e9f0151 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentFormController.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentFormController.php
@@ -87,6 +87,9 @@ protected function init(array &$form_state) {
   public function form(array $form, array &$form_state) {
     /** @var \Drupal\comment\CommentInterface $comment */
     $comment = $this->entity;
+
+    $form = parent::form($form, $form_state, $comment);
+
     $entity = $this->entityManager->getStorage($comment->getCommentedEntityTypeId())->load($comment->getCommentedEntityId());
     $field_name = $comment->getFieldName();
     $instance = $this->fieldInfo->getInstance($entity->getEntityTypeId(), $entity->bundle(), $field_name);
@@ -209,13 +212,10 @@ public function form(array $form, array &$form_state) {
       '#access' => $is_admin,
     );
 
-    $form['subject'] = array(
-      '#type' => 'textfield',
-      '#title' => $this->t('Subject'),
-      '#maxlength' => 64,
-      '#default_value' => $comment->getSubject(),
+    $form['subject'] += array(
       '#access' => $instance->getSetting('subject'),
     );
+    unset($form['subject']['widget'][0]['value']['#description']);
 
     // Used for conditional validation of author fields.
     $form['is_anonymous'] = array(
@@ -230,7 +230,7 @@ public function form(array $form, array &$form_state) {
       $form[$key] = array('#type' => 'value', '#value' => $original->$key->{$key_name});
     }
 
-    return parent::form($form, $form_state, $comment);
+    return $form;
   }
 
   /**
diff --git a/core/modules/comment/lib/Drupal/comment/Entity/Comment.php b/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
index 6ec3e82..4192669 100644
--- a/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
+++ b/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
@@ -235,7 +235,11 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
     $fields['subject'] = FieldDefinition::create('string')
       ->setLabel(t('Subject'))
       ->setDescription(t('The comment title or subject.'))
-      ->setSetting('max_length', 64);
+      ->setSetting('max_length', 64)
+      ->setDisplayOptions('form', array(
+        'type' => 'string',
+        'weight' => 0,
+      ));
 
     $fields['uid'] = FieldDefinition::create('entity_reference')
       ->setLabel(t('User ID'))
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentAnonymousTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentAnonymousTest.php
index f71619b..580ee56 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentAnonymousTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentAnonymousTest.php
@@ -69,7 +69,7 @@ function testAnonymous() {
     $edit = array(
       'name' => $this->admin_user->getUsername(),
       'mail' => $this->randomName() . '@example.com',
-      'subject' => $this->randomName(),
+      'subject[0][value]' => $this->randomName(),
       'comment_body[0][value]' => $this->randomName(),
     );
     $this->drupalPostForm('comment/reply/node/' . $this->node->id() . '/comment', $edit, t('Save'));
@@ -137,7 +137,7 @@ function testAnonymous() {
     // Attempt to view node-comment form while disallowed.
     $this->drupalGet('comment/reply/node/' . $this->node->id() . '/comment');
     $this->assertText('You are not authorized to post comments', 'Error attempting to post comment.');
-    $this->assertNoFieldByName('subject', '', 'Subject field not found.');
+    $this->assertNoFieldByName('subject[0][value]', '', 'Subject field not found.');
     $this->assertNoFieldByName('comment_body[0][value]', '', 'Comment field not found.');
 
     user_role_change_permissions(DRUPAL_ANONYMOUS_RID, array(
@@ -157,7 +157,7 @@ function testAnonymous() {
     ));
     $this->drupalGet('node/' . $this->node->id());
     $this->assertNoPattern('@<h2[^>]*>Comments</h2>@', 'Comments were not displayed.');
-    $this->assertFieldByName('subject', '', 'Subject field found.');
+    $this->assertFieldByName('subject[0][value]', '', 'Subject field found.');
     $this->assertFieldByName('comment_body[0][value]', '', 'Comment field found.');
 
     $this->drupalGet('comment/reply/node/' . $this->node->id() . '/comment/' . $anonymous_comment3->id());
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentLanguageTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentLanguageTest.php
index 139bf73..b7eddb4 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentLanguageTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentLanguageTest.php
@@ -109,7 +109,7 @@ function testCommentLanguage() {
         $prefix = empty($prefixes[$langcode]) ? '' : $prefixes[$langcode] . '/';
         $comment_values[$node_langcode][$langcode] = $this->randomName();
         $edit = array(
-          'subject' => $this->randomName(),
+          'subject[0][value]' => $this->randomName(),
           'comment_body[0][value]' => $comment_values[$node_langcode][$langcode],
         );
         $this->drupalPostForm($prefix . 'node/' . $node->id(), $edit, t('Preview'));
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentNonNodeTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentNonNodeTest.php
index d4af65e..5b67a28 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentNonNodeTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentNonNodeTest.php
@@ -98,10 +98,10 @@ function postComment(EntityInterface $entity, $comment, $subject = '', $contact
     }
 
     if ($subject_mode == TRUE) {
-      $edit['subject'] = $subject;
+      $edit['subject[0][value]'] = $subject;
     }
     else {
-      $this->assertNoFieldByName('subject', '', 'Subject field not found.');
+      $this->assertNoFieldByName('subject[0][value]', '', 'Subject field not found.');
     }
 
     if ($contact !== NULL && is_array($contact)) {
@@ -297,7 +297,7 @@ function testCommentFunctionality() {
     // Attempt to view test entity comment form while disallowed.
     $this->drupalGet('comment/reply/entity_test/' . $this->entity->id() . '/comment');
     $this->assertText('You are not authorized to post comments', 'Error attempting to post comment.');
-    $this->assertNoFieldByName('subject', '', 'Subject field not found.');
+    $this->assertNoFieldByName('subject[0][value]', '', 'Subject field not found.');
     $this->assertNoFieldByName('comment_body[0][value]', '', 'Comment field not found.');
 
     user_role_change_permissions(DRUPAL_ANONYMOUS_RID, array(
@@ -310,7 +310,7 @@ function testCommentFunctionality() {
     $this->assertPattern('@<h2[^>]*>Comments</h2>@', 'Comments were displayed.');
     $this->assertLink('Log in', 0, 'Link to log in was found.');
     $this->assertLink('register', 0, 'Link to register was found.');
-    $this->assertNoFieldByName('subject', '', 'Subject field not found.');
+    $this->assertNoFieldByName('subject[0][value]', '', 'Subject field not found.');
     $this->assertNoFieldByName('comment_body[0][value]', '', 'Comment field not found.');
 
     // Test the combination of anonymous users being able to post, but not view
@@ -324,7 +324,7 @@ function testCommentFunctionality() {
     ));
     $this->drupalGet('entity_test/' . $this->entity->id());
     $this->assertNoPattern('@<h2[^>]*>Comments</h2>@', 'Comments were not displayed.');
-    $this->assertFieldByName('subject', '', 'Subject field found.');
+    $this->assertFieldByName('subject[0][value]', '', 'Subject field found.');
     $this->assertFieldByName('comment_body[0][value]', '', 'Comment field found.');
 
     $this->drupalGet('comment/reply/entity_test/' . $this->entity->id() . '/comment/' . $comment1->id());
@@ -373,7 +373,7 @@ function testCommentFunctionality() {
     $this->assertNoField('edit-field-foobar-0-status-0');
 
     $this->drupalGet('comment/reply/entity_test/comment/' . $new_entity->id());
-    $this->assertNoFieldByName('subject', '', 'Subject field found.');
+    $this->assertNoFieldByName('subject[0][value]', '', 'Subject field found.');
     $this->assertNoFieldByName('comment_body[0][value]', '', 'Comment field found.');
   }
 
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
index 1de62da..fbd29b5 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
@@ -54,17 +54,17 @@ function testCommentPreview() {
 
     // As the web user, fill in the comment form and preview the comment.
     $edit = array();
-    $edit['subject'] = $this->randomName(8);
+    $edit['subject[0][value]'] = $this->randomName(8);
     $edit['comment_body[0][value]'] = $this->randomName(16);
     $this->drupalPostForm('node/' . $this->node->id(), $edit, t('Preview'));
 
     // Check that the preview is displaying the title and body.
     $this->assertTitle(t('Preview comment | Drupal'), 'Page title is "Preview comment".');
-    $this->assertText($edit['subject'], 'Subject displayed.');
+    $this->assertText($edit['subject[0][value]'], 'Subject displayed.');
     $this->assertText($edit['comment_body[0][value]'], 'Comment displayed.');
 
     // Check that the title and body fields are displayed with the correct values.
-    $this->assertFieldByName('subject', $edit['subject'], 'Subject field displayed.');
+    $this->assertFieldByName('subject[0][value]', $edit['subject[0][value]'], 'Subject field displayed.');
     $this->assertFieldByName('comment_body[0][value]', $edit['comment_body[0][value]'], 'Comment field displayed.');
 
     // Check that the signature is displaying with the correct text format.
@@ -87,7 +87,7 @@ function testCommentEditPreviewSave() {
 
     $edit = array();
     $date = new DrupalDateTime('2008-03-02 17:23');
-    $edit['subject'] = $this->randomName(8);
+    $edit['subject[0][value]'] = $this->randomName(8);
     $edit['comment_body[0][value]'] = $this->randomName(16);
     $edit['name'] = $web_user->getUsername();
     $edit['date[date]'] = $date->format('Y-m-d');
@@ -96,18 +96,18 @@ function testCommentEditPreviewSave() {
     $expected_text_date = format_date($raw_date);
     $expected_form_date = $date->format('Y-m-d');
     $expected_form_time = $date->format('H:i:s');
-    $comment = $this->postComment($this->node, $edit['subject'], $edit['comment_body[0][value]'], TRUE);
+    $comment = $this->postComment($this->node, $edit['subject[0][value]'], $edit['comment_body[0][value]'], TRUE);
     $this->drupalPostForm('comment/' . $comment->id() . '/edit', $edit, t('Preview'));
 
     // Check that the preview is displaying the subject, comment, author and date correctly.
     $this->assertTitle(t('Preview comment | Drupal'), 'Page title is "Preview comment".');
-    $this->assertText($edit['subject'], 'Subject displayed.');
+    $this->assertText($edit['subject[0][value]'], 'Subject displayed.');
     $this->assertText($edit['comment_body[0][value]'], 'Comment displayed.');
     $this->assertText($edit['name'], 'Author displayed.');
     $this->assertText($expected_text_date, 'Date displayed.');
 
     // Check that the subject, comment, author and date fields are displayed with the correct values.
-    $this->assertFieldByName('subject', $edit['subject'], 'Subject field displayed.');
+    $this->assertFieldByName('subject[0][value]', $edit['subject[0][value]'], 'Subject field displayed.');
     $this->assertFieldByName('comment_body[0][value]', $edit['comment_body[0][value]'], 'Comment field displayed.');
     $this->assertFieldByName('name', $edit['name'], 'Author field displayed.');
     $this->assertFieldByName('date[date]', $edit['date[date]'], 'Date field displayed.');
@@ -119,7 +119,7 @@ function testCommentEditPreviewSave() {
 
     // Check that the comment fields are correct after loading the saved comment.
     $this->drupalGet('comment/' . $comment->id() . '/edit');
-    $this->assertFieldByName('subject', $edit['subject'], 'Subject field displayed.');
+    $this->assertFieldByName('subject[0][value]', $edit['subject[0][value]'], 'Subject field displayed.');
     $this->assertFieldByName('comment_body[0][value]', $edit['comment_body[0][value]'], 'Comment field displayed.');
     $this->assertFieldByName('name', $edit['name'], 'Author field displayed.');
     $this->assertFieldByName('date[date]', $expected_form_date, 'Date field displayed.');
@@ -127,7 +127,7 @@ function testCommentEditPreviewSave() {
 
     // Submit the form using the displayed values.
     $displayed = array();
-    $displayed['subject'] = (string) current($this->xpath("//input[@id='edit-subject']/@value"));
+    $displayed['subject[0][value]'] = (string) current($this->xpath("//input[@id='edit-subject-0-value']/@value"));
     $displayed['comment_body[0][value]'] = (string) current($this->xpath("//textarea[@id='edit-comment-body-0-value']"));
     $displayed['name'] = (string) current($this->xpath("//input[@id='edit-name']/@value"));
     $displayed['date[date]'] = (string) current($this->xpath("//input[@id='edit-date-date']/@value"));
@@ -136,7 +136,7 @@ function testCommentEditPreviewSave() {
 
     // Check that the saved comment is still correct.
     $comment_loaded = comment_load($comment->id(), TRUE);
-    $this->assertEqual($comment_loaded->getSubject(), $edit['subject'], 'Subject loaded.');
+    $this->assertEqual($comment_loaded->getSubject(), $edit['subject[0][value]'], 'Subject loaded.');
     $this->assertEqual($comment_loaded->comment_body->value, $edit['comment_body[0][value]'], 'Comment body loaded.');
     $this->assertEqual($comment_loaded->getAuthorName(), $edit['name'], 'Name loaded.');
     $this->assertEqual($comment_loaded->getCreatedTime(), $raw_date, 'Date loaded.');
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentTestBase.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentTestBase.php
index c1edf13..3edad1d 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentTestBase.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentTestBase.php
@@ -119,10 +119,10 @@ public function postComment($entity, $comment, $subject = '', $contact = NULL, $
     }
 
     if ($subject_mode == TRUE) {
-      $edit['subject'] = $subject;
+      $edit['subject[0][value]'] = $subject;
     }
     else {
-      $this->assertNoFieldByName('subject', '', 'Subject field not found.');
+      $this->assertNoFieldByName('subject[0][value]', '', 'Subject field not found.');
     }
 
     if ($contact !== NULL && is_array($contact)) {
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentTranslationUITest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentTranslationUITest.php
index 5e5b4de..b971a6f 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentTranslationUITest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentTranslationUITest.php
@@ -119,7 +119,7 @@ protected function createEntity($values, $langcode, $node_bundle = 'node__commen
   protected function getNewEntityValues($langcode) {
     // Comment subject is not translatable hence we use a fixed value.
     return array(
-      'subject' => $this->subject,
+      'subject' => array(array('value' => $this->subject)),
       'comment_body' => array(array('value' => $this->randomName(16))),
     ) + parent::getNewEntityValues($langcode);
   }
diff --git a/core/modules/config_translation/lib/Drupal/config_translation/Tests/ConfigTranslationUiTest.php b/core/modules/config_translation/lib/Drupal/config_translation/Tests/ConfigTranslationUiTest.php
index 405aaf5..9aa1a1c 100644
--- a/core/modules/config_translation/lib/Drupal/config_translation/Tests/ConfigTranslationUiTest.php
+++ b/core/modules/config_translation/lib/Drupal/config_translation/Tests/ConfigTranslationUiTest.php
@@ -299,7 +299,7 @@ public function testContactConfigEntityTranslation() {
 
       // Submit feedback.
       $edit = array(
-        'subject' => 'Test subject',
+        'subject[0][value]' => 'Test subject',
         'message' => 'Test message',
       );
       $this->drupalPostForm(NULL, $edit, t('Send message'));
diff --git a/core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php b/core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php
index 6373929..09f8d29 100644
--- a/core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php
+++ b/core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php
@@ -455,7 +455,7 @@ function testForumWithNewPost() {
     $this->drupalLogin($this->post_comment_user);
     // Post a reply to the topic.
     $edit = array();
-    $edit['subject'] = $this->randomName();
+    $edit['subject[0][value]'] = $this->randomName();
     $edit['comment_body[0][value]'] = $this->randomName();
     $this->drupalPostForm('node/' . $node->id(), $edit, t('Save'));
     $this->assertResponse(200);
diff --git a/core/modules/rdf/lib/Drupal/rdf/Tests/TrackerAttributesTest.php b/core/modules/rdf/lib/Drupal/rdf/Tests/TrackerAttributesTest.php
index fa7f673..c6d52c1 100644
--- a/core/modules/rdf/lib/Drupal/rdf/Tests/TrackerAttributesTest.php
+++ b/core/modules/rdf/lib/Drupal/rdf/Tests/TrackerAttributesTest.php
@@ -168,7 +168,7 @@ function _testBasicTrackerRdfaMarkup(NodeInterface $node) {
 
     // Adds new comment to ensure the tracker is updated accordingly.
     $comment = array(
-      'subject' => $this->randomName(),
+      'subject[0][value]' => $this->randomName(),
       'comment_body[0][value]' => $this->randomName(),
     );
     $this->drupalPostForm('comment/reply/node/' . $node->id() .'/comment', $comment, t('Save'));
diff --git a/core/modules/search/lib/Drupal/search/Tests/SearchRankingTest.php b/core/modules/search/lib/Drupal/search/Tests/SearchRankingTest.php
index 5d16f80..895c0f0 100644
--- a/core/modules/search/lib/Drupal/search/Tests/SearchRankingTest.php
+++ b/core/modules/search/lib/Drupal/search/Tests/SearchRankingTest.php
@@ -87,7 +87,7 @@ public function testRankings() {
 
     // Add a comment to one of the nodes.
     $edit = array();
-    $edit['subject'] = 'my comment title';
+    $edit['subject[0][value]'] = 'my comment title';
     $edit['comment_body[0][value]'] = 'some random comment';
     $this->drupalGet('comment/reply/node/' . $nodes['comments'][1]->id() . '/comment');
     $this->drupalPostForm(NULL, $edit, t('Preview'));
diff --git a/core/modules/tracker/lib/Drupal/tracker/Tests/TrackerTest.php b/core/modules/tracker/lib/Drupal/tracker/Tests/TrackerTest.php
index 001de20..560d530 100644
--- a/core/modules/tracker/lib/Drupal/tracker/Tests/TrackerTest.php
+++ b/core/modules/tracker/lib/Drupal/tracker/Tests/TrackerTest.php
@@ -108,7 +108,7 @@ function testTrackerUser() {
       'status' => 1,
     ));
     $comment = array(
-      'subject' => $this->randomName(),
+      'subject[0][value]' => $this->randomName(),
       'comment_body[0][value]' => $this->randomName(20),
     );
     $this->drupalPostForm('comment/reply/node/' . $other_published_my_comment->id() . '/comment', $comment, t('Save'));
@@ -186,7 +186,7 @@ function testTrackerNewComments() {
 
     // Add a comment to the page.
     $comment = array(
-      'subject' => $this->randomName(),
+      'subject[0][value]' => $this->randomName(),
       'comment_body[0][value]' => $this->randomName(20),
     );
     $this->drupalPostForm('comment/reply/node/' . $node->id() . '/comment', $comment, t('Save'));
@@ -207,7 +207,7 @@ function testTrackerNewComments() {
 
     // Add another comment as other_user.
     $comment = array(
-      'subject' => $this->randomName(),
+      'subject[0][value]' => $this->randomName(),
       'comment_body[0][value]' => $this->randomName(20),
     );
     // If the comment is posted in the same second as the last one then Drupal
@@ -239,7 +239,7 @@ function testTrackerCronIndexing() {
     // Add a comment to the last node as other user.
     $this->drupalLogin($this->other_user);
     $comment = array(
-      'subject' => $this->randomName(),
+      'subject[0][value]' => $this->randomName(),
       'comment_body[0][value]' => $this->randomName(20),
     );
     $this->drupalPostForm('comment/reply/node/' . $nodes[3]->id() . '/comment', $comment, t('Save'));
diff --git a/core/modules/user/lib/Drupal/user/Tests/UserCancelTest.php b/core/modules/user/lib/Drupal/user/Tests/UserCancelTest.php
index edd4ea1..12dcb86 100644
--- a/core/modules/user/lib/Drupal/user/Tests/UserCancelTest.php
+++ b/core/modules/user/lib/Drupal/user/Tests/UserCancelTest.php
@@ -319,13 +319,13 @@ function testUserDelete() {
 
     // Create comment.
     $edit = array();
-    $edit['subject'] = $this->randomName(8);
+    $edit['subject[0][value]'] = $this->randomName(8);
     $edit['comment_body[0][value]'] = $this->randomName(16);
 
     $this->drupalPostForm('comment/reply/node/' . $node->id() . '/comment', $edit, t('Preview'));
     $this->drupalPostForm(NULL, array(), t('Save'));
     $this->assertText(t('Your comment has been posted.'));
-    $comments = entity_load_multiple_by_properties('comment', array('subject' => $edit['subject']));
+    $comments = entity_load_multiple_by_properties('comment', array('subject' => $edit['subject[0][value]']));
     $comment = reset($comments);
     $this->assertTrue($comment->id(), 'Comment found.');
 
diff --git a/core/modules/user/lib/Drupal/user/Tests/UserSignatureTest.php b/core/modules/user/lib/Drupal/user/Tests/UserSignatureTest.php
index 74a1712..7bf405f 100644
--- a/core/modules/user/lib/Drupal/user/Tests/UserSignatureTest.php
+++ b/core/modules/user/lib/Drupal/user/Tests/UserSignatureTest.php
@@ -102,7 +102,7 @@ function testUserSignature() {
 
     // Create a comment.
     $edit = array();
-    $edit['subject'] = $this->randomName(8);
+    $edit['subject[0][value]'] = $this->randomName(8);
     $edit['comment_body[0][value]'] = $this->randomName(16);
     $this->drupalPostForm('comment/reply/node/' . $node->id() .'/comment', $edit, t('Preview'));
     $this->drupalPostForm(NULL, array(), t('Save'));