diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index ad82046..c2a2ae6 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -613,6 +613,7 @@ function template_preprocess_comment(&$variables) {
   $commented_entity = $comment->getCommentedEntity();
   $variables['comment'] = $comment;
   $variables['commented_entity'] = $commented_entity;
+  $variables['threaded'] = $variables['elements']['#comment_threaded'];
 
   $account = $comment->getOwner();
   $username = array(
diff --git a/core/modules/comment/templates/comment.html.twig b/core/modules/comment/templates/comment.html.twig
index 3a7d19b..31b82e2 100644
--- a/core/modules/comment/templates/comment.html.twig
+++ b/core/modules/comment/templates/comment.html.twig
@@ -41,6 +41,7 @@
  * - content_attributes: List of classes for the styling of the comment content.
  * - title_attributes: Same as attributes, except applied to the main title
  *   tag that appears in the template.
+ * - threaded: A flag indicating whether the comments are threaded or not.
  *
  * These variables are provided to give context about the parent comment (if
  * any):
diff --git a/core/themes/bartik/templates/comment.html.twig b/core/themes/bartik/templates/comment.html.twig
index 31b9a77..2dac831 100644
--- a/core/themes/bartik/templates/comment.html.twig
+++ b/core/themes/bartik/templates/comment.html.twig
@@ -41,6 +41,7 @@
  * - title_attributes: Same as attributes, except applied to the main title
  *   tag that appears in the template.
  * - content_attributes: List of classes for the styling of the comment content.
+ * - threaded: A flag indicating whether the comments are threaded or not.
  *
  * These variables are provided to give context about the parent comment (if
  * any):
@@ -63,7 +64,9 @@
  * @see template_preprocess_comment()
  */
 #}
-{{ attach_library('classy/drupal.comment.threaded') }}
+{% if threaded %}
+  {{ attach_library('classy/drupal.comment.threaded') }}
+{% endif %}
 {%
   set classes = [
     'comment',
diff --git a/core/themes/classy/templates/content/comment.html.twig b/core/themes/classy/templates/content/comment.html.twig
index 1decd44..bb06364 100644
--- a/core/themes/classy/templates/content/comment.html.twig
+++ b/core/themes/classy/templates/content/comment.html.twig
@@ -41,6 +41,7 @@
  * - content_attributes: List of classes for the styling of the comment content.
  * - title_attributes: Same as attributes, except applied to the main title
  *   tag that appears in the template.
+ * - threaded: A flag indicating whether the comments are threaded or not.
  *
  * These variables are provided to give context about the parent comment (if
  * any):
@@ -63,7 +64,9 @@
  * @see template_preprocess_comment()
  */
 #}
-{{ attach_library('classy/drupal.comment.threaded') }}
+{% if threaded %}
+  {{ attach_library('classy/drupal.comment.threaded') }}
+{% endif %}
 {%
   set classes = [
     'comment',