Alright friends, you can now consider whatever you think is trustworthy. You can't force me to sign messages from the same bitcoin address the OP has, now only he has it.
So your story is you left the unencrypted key for your forum bitcoin address on a thumb drive, it got stolen, and now the thief is using it to claim ownership of your account?
I also don't design signatures and logos, that's not my skill, it's a skill I paid for in the past.
But you were involved in signature design contests -- so you were outsourcing your design entries?
One other thing: do these accounts mean anything to you?
Mr.sprin
amihada
Frankly I don't believe either one of you. The simplest explanation is the most likely, which is the account was sold & the original owner is trying to take it back.