BuddyPress.org

This one buddy press bug :

wordpress : 4.9.5
Buddypress : 2.9.4

On registration time same like default wordpress username allowed with space but buddy presss remove a space in code.

\plugins\buddypress\bp-members\bp-members-functions.php Line : 1852

$user_login     = preg_replace( '/\s+/', '', sanitize_user( $user_login, true ) );

Prevent spaces in WordPress/BuddyPress Usernames

In short without validate filed why removed a space from username because of after registration user don’t know this one removed a space.

Example :
Ravi Patel (registration input time)
After registration this one display now in backend RaviPatel.