<!-- BEGIN COPY / PASTE -->
    function disable_comments_post_types_support() {
      $post_types = get_post_types();
      foreach ($post_types as $post_type) {
        if (post_type_supports($post_type, 'comments')) {
          remove_post_type_support($post_type, 'comments');
          remove_post_type_support($post_type, 'trackbacks');
        }
      }
    }
    add_action('admin_init', 'disable_comments_post_types_support');

    function disable_comments_status() {
      return false;
    }
    add_filter('comments_open', 'disable_comments_status', 20, 2);
    add_filter('pings_open', 'disable_comments_status', 20, 2);

    function disable_comments_admin_menu() {
      remove_menu_page('edit-comments.php');
    }
    add_action('admin_menu', 'disable_comments_admin_menu');
    <!-- END COPY / PASTE -->