Find an BTC address posted by the account. Sign a message to confirm ownership. To do so, read this thread: https://bitcointalk.org/index.php?topic=703657.0. Optionally post it here and I will neg. rate the account until recovered.
what address, where? I never posted any BTC addresses here.
Then you're likely out of luck. You have to provide sufficient proof that you are the original owner of the account kiffner.
Is there any other way to prove I am owner of that account?