roonex

You can set default widgets for multisite but you have to edit wp_install_defaults functions in wp-admin/includes/upgrade.php.

There you can replace update_option( ‘sidebars_widgets’….. row with something like this:

update_option( 'sidebars_widgets', array ( 'wp_inactive_widgets' => array ( ), 'primary-widget-area' => array ( 0 => 'widget-id-base-2', 1 => 'widget2-id-base-2', 2 => 'widget3-id-base-2', 3 => 'widget4-id-base-2', 4 => 'widget5-id-base-2', ), 'secondary-widget-area' => array ( ), 'first-footer-widget-area' => array ( ), 'second-footer-widget-area' => array ( ), 'third-footer-widget-area' => array ( ), 'fourth-footer-widget-area' => array ( ), 'array_version' => 3 ) );

It is not blank, it is with spaces…this is a bug in wp and this plugin too.
If you want to restrict this type of usernames you have to modify the plugin. In this thread I explain how to do it:
https://www.ads-software.com/support/topic/213474?replies=1