diff -u b/core/modules/comment/tests/modules/comment_test/src/CommentTestSqlEntityStorage.php b/core/modules/comment/tests/modules/comment_test/src/CommentTestSqlEntityStorage.php
--- b/core/modules/comment/tests/modules/comment_test/src/CommentTestSqlEntityStorage.php
+++ b/core/modules/comment/tests/modules/comment_test/src/CommentTestSqlEntityStorage.php
@@ -16,8 +16,8 @@
    * author) invalid, in the SQL storage backend.
    *
    * @param array $comment_ids
-   *   IDs of comments to orphan. If not provided, one comment will be taken
-   *   semi randomly.
+   *   IDs of comments to orphan. If empty, one comment will be taken semi
+   *   randomly.
    * @param array $fields
    *   Names of fields to change. Allowed values: 'pid', 'entity_id', 'uid'. If
    *   not provided, all fields will be changed.
diff -u b/core/modules/comment/tests/src/Functional/CommentOrphanedTest.php b/core/modules/comment/tests/src/Functional/CommentOrphanedTest.php
--- b/core/modules/comment/tests/src/Functional/CommentOrphanedTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentOrphanedTest.php
@@ -2,20 +2,22 @@
 
 namespace Drupal\Tests\comment\Functional;
 
+use Drupal\Core\Entity\Sql\SqlEntityStorageInterface;
+
 /**
  * Tests operations on orphaned comments.
  *
- * Drupal core will officially never orphan comments. An orphan comment is
- * comment with a nonexistent parent comment or commented entities.
+ * An orphan comment is a comment with a nonexistent parent comment or commented
+ * entity. Drupal core should never orphan comments.
  *
  * This test exists despite the above because it's expected that in time someone
  * will try to be smart and delete old entities/comments from a large database,
  * a PHP process will die at exactly the wrong time, or whatever exotic event
  * happens that makes comments with invalid parent/entity references exist. When
  * this happens, a site should not start crashing during basic operations like
- * loading/displaying a node page. Practice has shown that it's fairly easy to
+ * loading/displaying a node page. Experience has shown that it's fairly easy to
  * inadvertently write code that makes Drupal crash during loading/rendering
- * orphaned comments; this test will draw attention to that code in Drupal core.
+ * orphaned comments. This test draws attention to such code in Drupal core.
  *
  * @group comment
  */
@@ -46,53 +48,51 @@
 
     // We only know how to orphan comments on SQL based entity storage.
     $storage = $manager->getStorage('comment');
-    if (in_array('Drupal\Core\Entity\Sql\SqlEntityStorageInterface', class_implements($storage))) {
-      $session = $this->assertSession();
+    $this->assertInstanceOf(SqlEntityStorageInterface::class, $storage);
+
+    $session = $this->assertSession();
 
-      // Make sure we have a comment.
-      $this->drupalLogin($this->webUser);
-      $comment_text = $this->randomMachineName();
-      $subject = $this->randomMachineName();
-      $this->postComment($this->node, $comment_text, $subject);
-
-      $this->drupalGet('node/2');
-      $this->drupalGet('node/' . $this->node->id());
-      $session->pageTextContains($comment_text);
-      $session->pageTextContains($subject);
-
-      // Make the comment an orphan.
-      $original_class = get_class($storage);
-      $manager->clearCachedDefinitions();
-      $manager->getDefinition('comment')
-        ->setStorageClass('Drupal\comment_test\CommentTestSqlEntityStorage');
-
-      $storage = $manager->getStorage('comment');
-      // Invalidate the author/parent comment, not the commented entity.
-      $storage->orphanComments([], ['pid', 'uid']);
-
-      // Render the entity, with orphaned comment, implicitly testing that
-      // nothing breaks.
-      $this->drupalGet('node/' . $this->node->id());
-      $session->pageTextContains($comment_text);
-      $session->pageTextContains($subject);
-
-      $ids = $storage->orphanComments();
-
-      // Load, render (standalone without commented entity) and delete comments,
-      // implicitly testing that nothing breaks when the commented entity is not
-      // available. This does not have a current practical application (there
-      // are no standalone 'comment pages') but it ensures some decoupling of
-      // the comment view/render code, which is a good thing in itself.
-      $entities = $storage->loadMultiple($ids);
-      $storage->delete($entities);
-      $manager->clearCachedDefinitions();
-      $manager->getDefinition('comment')->setStorageClass($original_class);
-
-      $this->drupalGet('node/' . $this->node->id());
-      $session->pageTextNotContains($comment_text);
-      $session->pageTextNotContains($subject);
-    }
+    // Make sure we have a comment.
+    $this->drupalLogin($this->webUser);
+    $comment_text = $this->randomMachineName();
+    $subject = $this->randomMachineName();
+    $this->postComment($this->node, $comment_text, $subject);
+
+    $this->drupalGet('node/' . $this->node->id());
+    $session->pageTextContains($comment_text);
+    $session->pageTextContains($subject);
+
+    // Make the comment an orphan.
+    $original_class = get_class($storage);
+    $manager->clearCachedDefinitions();
+    $manager->getDefinition('comment')
+      ->setStorageClass('Drupal\comment_test\CommentTestSqlEntityStorage');
+
+    $storage = $manager->getStorage('comment');
+    // Invalidate the author/parent comment, not the commented entity.
+    $storage->orphanComments([], ['pid', 'uid']);
 
+    // Render the entity, with orphaned comment, implicitly testing that
+    // nothing breaks.
+    $this->drupalGet('node/' . $this->node->id());
+    $session->pageTextContains($comment_text);
+    $session->pageTextContains($subject);
+
+    $ids = $storage->orphanComments();
+
+    // Load, render (standalone without commented entity) and delete comments,
+    // implicitly testing that nothing breaks when the commented entity is not
+    // available. This does not have a current practical application (there
+    // are no standalone 'comment pages') but it ensures some decoupling of
+    // the comment view/render code, which is a good thing in itself.
+    $entities = $storage->loadMultiple($ids);
+    $storage->delete($entities);
+    $manager->clearCachedDefinitions();
+    $manager->getDefinition('comment')->setStorageClass($original_class);
+
+    $this->drupalGet('node/' . $this->node->id());
+    $session->pageTextNotContains($comment_text);
+    $session->pageTextNotContains($subject);
   }
 
 }
diff -u b/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
--- b/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -237,9 +237,9 @@
       ->getPreparedFieldMapping('created');
     /** @var \Drupal\comment\CommentInterface $comment*/
     $comment->rdf_data['date'] = rdf_rdfa_attributes($created_mapping, $comment->get('created')->first()->toArray());
+    // The current function is a storage level hook, so avoid to bubble
+    // bubbleable metadata, because it can be outside of a render context.
     if ($entity = $comment->getCommentedEntity()) {
-      // The current function is a storage level hook, so avoid to bubble
-      // bubbleable metadata, because it can be outside of a render context.
       $comment->rdf_data['entity_uri'] = $entity->toUrl()->toString(TRUE)->getGeneratedUrl();
     }
     if ($parent = $comment->getParentComment()) {