It is, but not here and not in this case. My issues with Lauda also do not apply here, so asking for my assistence does not give you any bonus points just because they and I had a difficult history.

An account can be sold without leaving any publicly available data, thus proving an account has actually been sold is not possible. On the other hand it is easily possible to proof you are still the same person by proving a signed message. Either using your PGP key, should you have made one public, or using a bitcoin adress via which you have received funds in the past. Sometimes neither is possible, but this is only in the hands of the account owner. I tried my best in the past to make signing message as easily accessible to as many people as possible and other members have tried to make sure people "stake" an address for these cases.

With all said above, it is - of course - still possible to sell a private PGP or bitcoin key. Thus a signed message is no solid proof either. It is hover (or was, I am a bit out of touch) considered unlikely considering they keys are often used for other reasons as well.

tl;dr: I cant help you here, nor anyway else with similar issues. People will - out of spit or other reasons - dig into your history and try to find something they can use against you.