Please don't confuse Username and Nickname.

Please be familiar with Users Nickname, Username and Display Name differences, read this FAQ topic: https://wpforo.com/community/faq/nickname-vs-username-vs-display-names/

Yes, they are the same right after the registration, because WordPress creates user Nickname based on Username, but you can change the nickname in My Profile > Account page:

Nicknames are used for user @mentioning and in your profile URL. So again, this is the nickname not username:

https:// wpforo.com/community/profile/ hayguys0129/

Please read this post for more information: https://wpforo.com/community/postid/17315/

In any case, if you still want to disable nicknames and don't allow people to @menation each other, you should put this code in WordPress active theme functions.php file:

function wpforo_disable_user_nicenames( $nicename ){
   return '';
}
add_filter('wpforo_member_nicename', 'wpforo_disable_user_nicenames', 10);

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