Apparently, when a user applys and sets up their profile, they are allowed (on our board) to use the same username and display name.
In general, for security and other reasons, I think users are going to make a username that will not be as easy to read as the display name.
So, I think it would be helpful, if a user wrote "dr437uy" for their username and then was told they could not use that for their display name, they would sit back and actually come up with a good username.
