A few years back the Ed offered all Abers the opportunity to submit new Usernames which then replaced their originals; without any loss of question and answers which they had on record in the columns of Answerbank. It wasn't 100% successful because of those who applied some were unlucky with their requests to take-up the offer.
At present,it is the case that the only way you can change your username is if you re-register with a a different email address to that which you are currently using in AB.
Hello,
It is not currently possible to change usernames as this causes problems within the database - plus, it can be confusing because people won't know who you are anymore! If you would like a new username you would need to create a new account, but we would ask you to deactivate your current one as we only permit each person to have one account at a time.