commit 4cf3105ea72231f53215c28f4074c42a28334702
Author: Joel Pittet <joel@pittet.ca>
Date:   Tue Dec 3 18:21:20 2013 -0800

    revert the global  change

diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 38647b5..13b40b8 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -1509,8 +1509,7 @@ function template_preprocess_comment(&$variables) {
  *   HTML for a "you can't post comments" notice.
  */
 function comment_forbidden_message(EntityInterface $entity, $field_name) {
-
-  $user = \Drupal::currentUser();
+  global $user;
 
   // Since this is expensive to compute, we cache it so that a page with many
   // comments only has to query the database once for all the links.