theymos verified alia in /r/GirlsGoneBitcoin, so she had a kind of contact with him.
I think she probably just sent him a PM.
He has also written somewhere that he changes the username in some cases. But there must be a valid reason.Of course in must have a valid reason, cases like changes of essential information specially name changes might be subjected to a background check. To avoid abuse and being used as an advantage to trick others.