feature request:
having this History of Usernames to be searchable as "registered users" so if someone wants to register with a username that is in this list, he will not be able to, and will be required to contact the admin if this is an error...
the situation come often when someone register, and not remember his password or complete username, and instead of asking for a new access he register twice... that came at least 3 times here this year only...
something like "this username was once used by a user on this site. if you really need this username, please contact the admins. "... and this can be joined with the Ajax Alert...