It would be nice if there was something like a
name change history. Many users change their display names and then it becomes difficult to recognise them. So having such a feature will be certainly helpful.
Display changes are recorded, but your history is shown only to you, as of now. I see no harm in giving a user the option to make his username history publicly visible, but maybe thats just me. (PS: I'm not mimicking aking :P)
Enforcing public visibility would be considered a privacy infringement perhaps..