How did he change his name? Is it exclusive to VIPs? I know it's a different person, but how did he change his name?
VIPs can change their name themselves anytime they want to.
Others can ask theymos to change their names, and
Adding or removing text to/from a username is particularly likely to be accepted because it doesn't make it significantly easier for someone to scam. Your identity isn't really changed. I tend to ignore requests for complete username changes except from veteran members. (Even then, it's one of the lowest-priority requests I receive, so it can be forgotten. I have kind of a "leaky queue" for forum work -- if I don't get to a request in a couple of days, I usually drop it.)