I think they're missing the point, Twitter got the display name / username dichotomy right: Display Name: what everyone sees next to your username, no guarantees that you don't change it every 5 minutes though... username: something short you choose and change rarely, can be cool, memorable, fun, and quite creative, always unique [Real Name: who cares, often necessary for work tools even though email ought to be enou…
Twitter has some problems too. People do change their username, and every time they do, all previous tweets mentioning them by @username lead to dead ends.
But it may very well be for good reason. E.g. lets say an account is taken over by someone who changes the account into something suitably offensive after obtaining a lot of mentions. It would seem that treating a change as basically "this is a new account now" is the safest alternative in some respects.