increase number of special characters in member registration in WordPress

Hello
WordPress don’t accept member registration with special characters in username.

I used the following simple plugin to resolve this issue , it is OK but the issue that the maximum number of special characters is limited , member can use is 8 only.

How can I increase it?
thanks

<?php

/*

Plugin Name: WordPress Special Characters in Usernames

Plugin URI: https://www.oneall.com/

Description: Enables usernames containing special characters (russian, cyrillic, arabic) on your WordPress Blog

Version: 1.2

Author: Claude Schlesser

Author URI: https://www.oneall.com/

License: GPL2

*/

/**

 * Overrides the WordPress sanitize_user filter to allow special characters

 */

function wscu_sanitize_user ($username, $raw_username, $strict)

{

    //Strip HTML Tags

    $username = wp_strip_all_tags ($raw_username);

    //Remove Accents

    $username = remove_accents ($username);

    //Kill octets

    $username = preg_replace ('|%([a-fA-F0-9][a-fA-F0-9])|', '', $username);

    //Kill entities

    $username = preg_replace ('/&.+?;/', '', $username);

    //If strict, reduce to ASCII, Cyrillic and Arabic characters for max portability.

    if ($strict)

    {

        //Read settings

        $settings = get_option ('wscu_settings');

        //Replace

        $username = preg_replace ('|[^a-z\p{Arabic}\p{Cyrillic}0-9 _.\-@]|iu', '', $username);

    }

    //Remove Whitespaces

    $username = trim ($username);

    // Consolidate contiguous Whitespaces

    $username = preg_replace ('|\s+|', ' ', $username);

    //Done

    return $username;

}

add_filter ('sanitize_user', 'wscu_sanitize_user', 10, 3);