I think we should only allow like 1 username change per month. It's annoying when someone changes his username and then 40 minutes later has another and you are like "who is this?" *cough* Ironhide *cough*
But if not, at least something like the nudges where you can see who has changed their username, for example:
"SD8Z has changed his username to Daniel"
"The Elite has changed his username to RAF"
"Daniel has changed his username to SD8Z"
"Ironhide has changed his username to SomethingRandom"
"SomethingRandom has changed his username to OtherRandomThing"
But if not, at least something like the nudges where you can see who has changed their username, for example:
"SD8Z has changed his username to Daniel"
"The Elite has changed his username to RAF"
"Daniel has changed his username to SD8Z"
"Ironhide has changed his username to SomethingRandom"
"SomethingRandom has changed his username to OtherRandomThing"