They can always, forbid the creation of celebrity names. Just like you can't name a can of pop Pepsi, or Coke. That really wouldn't be that difficult for them.
I remember a couple of years ago after a school shooting, someone created an avi, with the name of the shooter, and was trolling PG sims with it. He was shut down in less than 3 hours. So they have the capability to not allow certain names, right from the start.