Early next year we will be allowing users to create a username with an underscore in it. They will be able to do this at account creation or by buying a name change. The new rule is that you can have one underscore in your name, but not at the beginning or the end. The username must be 3-20 characters long.

Please update your games to be ready for this change if username is a variable you’re relying on, or you are using underscores in some weird way. In general we suggest keying off UserID, because it won’t change.