Unpublishes a comment if it contains certain keywords.
Drupal\comment\Comment $comment: Comment object to modify.
array $context: Array with components:
comment_unpublish_by_keyword_action_form()
comment_unpublish_by_keyword_action_submit()
function comment_unpublish_by_keyword_action(Comment $comment, $context) {
  foreach ($context['keywords'] as $keyword) {
    $text = drupal_render($comment);
    if (strpos($text, $keyword) !== FALSE) {
      $comment->status = COMMENT_NOT_PUBLISHED;
      watchdog('action', 'Unpublished comment %subject.', array(
        '%subject' => $comment->subject,
      ));
      break;
    }
  }
}