I know for a fact that there are plenty of long-time members who almost practically resent their usernames.
Take me for instance. My first username here was "FatMarshall", but I ended up switching my emails around. Unaware that you can't change the WLID associated with the account, I was forced to make another account on Bungie.net with my new WLID, and since "FatMarshall" was taken at the time with my older WLID, "FatM" was birthed.
Will we ever be able to change our usernames in the future? Would you support such an addition or feature?