https://www.drupal.org/node/1962846

1962846-comment-wrapper.patch

diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 3c1ee17..ee258b1 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -139,9 +139,9 @@ function comment_theme() {
       'render element' => 'elements',
       'template' => 'comment',
     ),
-    'comment_wrapper' => array(
-      'render element' => 'content',
-      'template' => 'comment-wrapper',
+    'field__comment' => array(
+      'base hook' => 'field',
+      'template' => 'field--comment',
     ),
   );
 }
@@ -1209,31 +1209,34 @@ function template_preprocess_comment(&$variables) {
 }
 
 /**
- * Prepares variables for comment wrapper templates.
+ * Prepares variables for comment field templates.
  *
- * Default template: comment-wrapper.html.twig.
+ * Default template: field--comment.html.twig.
  *
  * @param array $variables
  *   An associative array containing:
- *   - content: An associative array containing render arrays for the list of
+ *   - element: An associative array containing render arrays for the list of
  *     comments, and the comment form. Array keys: comments, comment_form.
+ *
+ * @todo Rename to template_preprocess_field__comment() once
+ *   https://www.drupal.org/node/939462 is resolved.
  */
-function template_preprocess_comment_wrapper(&$variables) {
-  // Provide contextual information.
-  $variables['entity'] = $variables['content']['#entity'];
-  $variables['display_mode'] = $variables['content']['#display_mode'];
-
-  // 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'] = $variables['content']['comment_form'];
+function comment_preprocess_field(&$variables) {
+  $element = $variables['element'];
+  if ($element['#field_type'] == 'comment') {
+    // Provide contextual information.
+    $variables['comment_display_mode'] = $element[0]['#comment_display_mode'];
+    $variables['comment_type'] = $element[0]['#comment_type'];
+
+    // Adjust a comment field special variables.
+    $variables['attributes']['class'][] = 'comment-wrapper';
+    $variables['title_attributes']['class'][] = 'title';
+
+    // Create separate variables for the comments and comment form.
+    $variables['comments'] = $element[0]['comments'];
+    $variables['comment_form'] = $element[0]['comment_form'];
+    $variables['content_attributes']['class'] = array('title', 'comment-form__title');
+  }
 }
 
 /**
diff --git a/core/modules/comment/src/CommentManager.php b/core/modules/comment/src/CommentManager.php
index 1bed270..579034f 100644
--- a/core/modules/comment/src/CommentManager.php
+++ b/core/modules/comment/src/CommentManager.php
@@ -212,7 +212,7 @@ public function addDefaultField($entity_type, $bundle, $field_name = 'comment',
       // Set default to display comment list.
       entity_get_display($entity_type, $bundle, 'default')
         ->setComponent($field_name, array(
-          'label' => 'hidden',
+          'label' => 'above',
           'type' => 'comment_default',
           'weight' => 20,
         ))
diff --git a/core/modules/comment/src/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php b/core/modules/comment/src/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php
index 4597761..c7a0f11 100644
--- a/core/modules/comment/src/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php
+++ b/core/modules/comment/src/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php
@@ -218,9 +218,8 @@ public function viewElements(FieldItemListInterface $items) {
       }
 
       $elements[] = $output + array(
-        '#theme' => 'comment_wrapper__' . $entity->getEntityTypeId() . '__' . $entity->bundle() . '__' . $field_name,
-        '#entity' => $entity,
-        '#display_mode' => $this->getFieldSetting('default_mode'),
+        '#comment_type' => $this->getFieldSetting('comment_type'),
+        '#comment_display_mode' => $this->getFieldSetting('default_mode'),
         'comments' => array(),
         'comment_form' => array(),
       );
diff --git a/core/modules/comment/templates/comment-wrapper.html.twig b/core/modules/comment/templates/comment-wrapper.html.twig
deleted file mode 100644
index 52bb6b1..0000000
--- a/core/modules/comment/templates/comment-wrapper.html.twig
+++ /dev/null
@@ -1,52 +0,0 @@
-{#
-/**
- * @file
- * Default theme implementation for a comments container.
- *
- * Available variables:
- * - comments: List of comments rendered through comment.html.twig.
- * - form: The 'Add new comment' form.
- * - content: The content-related elements for the comment display. Use
- *   'content' to print them all, or print a subset such as
- *   'content.comment_form'.
- * - attributes: Remaining HTML attributes for the containing element.
- *   It includes the 'class' information, which includes:
- *   - comment-wrapper: The current template type, i.e., "theming hook".
- *   - title_prefix: Additional output populated by modules, intended to be
- *     displayed in front of the main title tag that appears in the template.
- *   - title_suffix: Additional title output populated by modules, intended to
- *     be displayed after the main title tag that appears in the template.
- *
- * The following variables are provided for contextual information.
- * - entity: The entity to which the comments belong.
- * - display_mode: The display mode for the comment listing, flat or threaded.
- *   The constants below show the possible values and should be used for
- *   comparison, as in the following example:
- *   @code
- *   {% if display_mode is constant('COMMENT_MODE_THREADED') %}
- *     <h3>{{ 'These comments are displayed in a threaded list.'|t }}</h3>
- *   {% endif %}
- *   @endcode
- *   - COMMENT_MODE_FLAT
- *   - COMMENT_MODE_THREADED
- *
- * @see template_preprocess_comment_wrapper()
- *
- * @ingroup themeable
- */
-#}
-<section{{ attributes }}>
-  {% if comments and (entity.entityType != 'node' or entity.bundle != 'forum') %}
-    {{ title_prefix }}
-    <h2 class="title">{{ 'Comments'|t }}</h2>
-    {{ title_suffix }}
-  {% endif %}
-
-  {{ comments }}
-
-  {% if form %}
-    <h2 class="title comment-form__title">{{ 'Add new comment'|t }}</h2>
-    {{ form }}
-  {% endif %}
-
-</section>
diff --git a/core/modules/comment/templates/field--comment.html.twig b/core/modules/comment/templates/field--comment.html.twig
new file mode 100644
index 0000000..7a2dbcb
--- /dev/null
+++ b/core/modules/comment/templates/field--comment.html.twig
@@ -0,0 +1,37 @@
+{#
+/**
+ * @file
+ * Default theme override for comment fields.
+ *
+ * Available variables:
+ * - attributes: HTML attributes for the containing element.
+ * - label_hidden: Whether to show the field label or not.
+ * - title_attributes: HTML attributes for the title.
+ * - label: The label for the field.
+ * - title_prefix: Additional output populated by modules, intended to be
+ *   displayed in front of the main title tag that appears in the template.
+ * - title_suffix: Additional title output populated by modules, intended to
+ *   be displayed after the main title tag that appears in the template.
+ * - comments: List of comments rendered through comment.html.twig.
+ * - content_attributes: HTML attributes for the form title.
+ * - comment_form: The 'Add new comment' form.
+ *
+ * @see template_preprocess_field()
+ * @see comment_preprocess_field()
+ */
+#}
+<section{{ attributes }}>
+  {% if comments and not label_hidden %}
+    {{ title_prefix }}
+    <h2{{ title_attributes }}>{{ label }}</h2>
+    {{ title_suffix }}
+  {% endif %}
+
+  {{ comments }}
+
+  {% if comment_form %}
+    <h2{{ content_attributes }}>{{ 'Add new comment'|t }}</h2>
+    {{ comment_form }}
+  {% endif %}
+
+</section>
diff --git a/core/modules/forum/forum.install b/core/modules/forum/forum.install
index 2b3d14f..6effde2 100644
--- a/core/modules/forum/forum.install
+++ b/core/modules/forum/forum.install
@@ -87,6 +87,14 @@ function forum_install() {
     ));
     if (empty($fields)) {
       Drupal::service('comment.manager')->addDefaultField('node', 'forum', 'comment_forum', CommentItemInterface::OPEN, 'comment_forum');
+      // Hide label for comment field.
+      entity_get_display('node', 'forum', 'default')
+        ->setComponent('comment_forum', array(
+          'label' => 'hidden',
+          'type' => 'comment_default',
+          'weight' => 20,
+        ))
+        ->save();
     }
   }
 }