diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 103c5c8..478dad1 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -1411,28 +1411,9 @@ function template_preprocess_comment(&$variables) {
     $variables['status'] = $comment->isPublished() ? 'published' : 'unpublished';
   }
 
-  // Gather comment classes.
-  $variables['attributes']['class'][] = 'comment';
-  // 'published' class is not needed, it is either 'preview' or 'unpublished'.
-  if ($variables['status'] != 'published') {
-    $variables['attributes']['class'][] = $variables['status'];
-  }
-  if (!$comment->getOwnerId()) {
-    $variables['attributes']['class'][] = 'by-anonymous';
-  }
-  else {
-    // @todo Use $entity->getAuthorId() after https://drupal.org/node/2078387
-    if ($commented_entity instanceof EntityOwnerInterface && $comment->getOwnerId() == $commented_entity->getOwnerId()) {
-      $variables['attributes']['class'][] = 'by-' . $commented_entity->getEntityTypeId() . '-author';
-    }
-  }
-  // Add clearfix class.
-  $variables['attributes']['class'][] = 'clearfix';
-
   // Add comment author user ID. Necessary for the comment-by-viewer library.
   $variables['attributes']['data-comment-user-id'] = $comment->getOwnerId();
 
-  $variables['content_attributes']['class'][] = 'content';
 }
 
 /**
@@ -1453,11 +1434,6 @@ function template_preprocess_comment_wrapper(&$variables) {
   // The comment form is optional and may not exist.
   $variables['content'] += array('comment_form' => array());
 
-  $variables['attributes']['id'] = 'comments';
-
-  // Add a comment wrapper class.
-  $variables['attributes']['class'][] = 'comment-wrapper';
-
   // Create separate variables for the comments and comment form.
   $variables['comments'] = $variables['content']['comments'];
   $variables['form'] = $variables['content']['comment_form'];
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentCSSTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentCSSTest.php
index 8c2df9b..bbca55e 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentCSSTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentCSSTest.php
@@ -93,24 +93,6 @@ function testCommentClasses() {
 
       // Verify classes if the comment is visible for the current user.
       if ($case['comment_status'] == CommentInterface::PUBLISHED || $case['user'] == 'admin') {
-        // Verify the by-anonymous class.
-        $comments = $this->xpath('//*[contains(@class, "comment") and contains(@class, "by-anonymous")]');
-        if ($case['comment_uid'] == 0) {
-          $this->assertTrue(count($comments) == 1, 'by-anonymous class found.');
-        }
-        else {
-          $this->assertFalse(count($comments), 'by-anonymous class not found.');
-        }
-
-        // Verify the by-node-author class.
-        $comments = $this->xpath('//*[contains(@class, "comment") and contains(@class, "by-node-author")]');
-        if ($case['comment_uid'] > 0 && $case['comment_uid'] == $case['node_uid']) {
-          $this->assertTrue(count($comments) == 1, 'by-node-author class found.');
-        }
-        else {
-          $this->assertFalse(count($comments), 'by-node-author class not found.');
-        }
-
         // Verify the data-comment-user-id attribute, which is used by the
         // drupal.comment-by-viewer library to add a by-viewer when the current
         // user (the viewer) was the author of the comment. We do this in Java-
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
index 1de62da..152e2ed 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
@@ -71,7 +71,7 @@ function testCommentPreview() {
     $this->assertLink($test_signature);
 
     // Check that the user picture is displayed.
-    $this->assertFieldByXPath("//article[contains(@class, 'preview')]//div[contains(@class, 'user-picture')]//img", NULL, 'User picture displayed.');
+    $this->assertFieldByXPath("//article//div[contains(@class, 'user-picture')]//img", NULL, 'User picture displayed.');
   }
 
   /**
diff --git a/core/modules/comment/templates/comment-wrapper.html.twig b/core/modules/comment/templates/comment-wrapper.html.twig
index b19c051..32661a2 100644
--- a/core/modules/comment/templates/comment-wrapper.html.twig
+++ b/core/modules/comment/templates/comment-wrapper.html.twig
@@ -35,17 +35,17 @@
  * @ingroup themeable
  */
 #}
-<section{{ attributes }}>
+<section class="comment-wrapper {{ attributes.class }}" {{ attributes }} id="comments">
   {% if comments and (entity.entityType != 'node' or entity.bundle != 'forum') %}
     {{ title_prefix }}
-    <h2 class="title">{{ 'Comments'|t }}</h2>
+    <h2>{% trans %}Comments{% endtrans %}</h2>
     {{ title_suffix }}
   {% endif %}
 
   {{ comments }}
 
   {% if form %}
-    <h2 class="title comment-form">{{ 'Add new comment'|t }}</h2>
+    <h2 class="title comment-form">{% trans %}Add new comment{% endtrans %}</h2>
     {{ form }}
   {% endif %}
 
diff --git a/core/modules/comment/templates/comment.html.twig b/core/modules/comment/templates/comment.html.twig
index 5fca73b..3a7d1a4 100644
--- a/core/modules/comment/templates/comment.html.twig
+++ b/core/modules/comment/templates/comment.html.twig
@@ -64,7 +64,11 @@
  * @ingroup themeable
  */
 #}
-<article{{ attributes }}>
+{% set cssclass %}
+comment comment--status-{{ status }}
+{% endset %}
+
+<article class="{{ cssclass }} {{attributes.css }}"{{ attributes }}>
   {{ title_prefix }}
 
   {#