The downside using 3rd party applications is that you can't choose your name or avatar, hence the reason why i play SuperMechs at the original site:
http://supermechs.com/The only solution for you, that i see, is that you create yourself a new SuperMechs account with preferred name and scrap the old account (since you can't change your name or avatar).
Creating new in-game account should create account in the forums also (same username & psw). If it won't do that, you'll just have to create new forum account also.
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Aeacus