Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/comment/comment.api.php

@@ -0,0 +1,49 @@
+<?php
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\comment\CommentInterface;
+use Drupal\Core\Url;
+
+/**
+ * @file
+ * Hooks provided by the Comment module.
+ */
+
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Alter the links of a comment.
+ *
+ * @param array &$links
+ *   A renderable array representing the comment links.
+ * @param \Drupal\comment\CommentInterface $entity
+ *   The comment being rendered.
+ * @param array &$context
+ *   Various aspects of the context in which the comment links are going to be
+ *   displayed, with the following keys:
+ *   - 'view_mode': the view mode in which the comment is being viewed
+ *   - 'langcode': the language in which the comment is being viewed
+ *   - 'commented_entity': the entity to which the comment is attached
+ *
+ * @see \Drupal\comment\CommentViewBuilder::renderLinks()
+ * @see \Drupal\comment\CommentViewBuilder::buildLinks()
+ */
+function hook_comment_links_alter(array &$links, CommentInterface $entity, array &$context) {
+  $links['mymodule'] = array(
+    '#theme' => 'links__comment__mymodule',
+    '#attributes' => array('class' => array('links', 'inline')),
+    '#links' => array(
+      'comment-report' => array(
+        'title' => t('Report'),
+        'url' => Url::fromRoute('comment_test.report', ['comment' => $entity->id()], ['query' => ['token' => \Drupal::getContainer()->get('csrf_token')->get("comment/{$entity->id()}/report")]]),
+      ),
+    ),
+  );
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */