Thanks for posting about this Jeff. Every time someone comes in with the username "Matt" for example, the chat gets pretty sidetracked as they're wondering if it's the Matt, someone else named Matt, or an impersonator.

Still a little torn on what to do, even requiring registration won't completely solve the problem. It will at least help a bit if say, they post on their Twitter account confirming they have registered a certain username at WP Chat.