<?php
/*
Plugin Name: Stop comments over 13k
Description: A security precaution to stop comments over 13k.
Version: 0.0.2
Author: WPEngine
Author URI: wpengine.com
License: GPLv2
*/
add_filter('pre_comment_content', 'wpengine_die_on_long_comment', 9999);

function wpengine_die_on_long_comment($text) {
  if (strlen($text) > 13000) wp_die('This comment is longer than the maximum allowed size and has been dropped.');
  return $text;
}