Not necessarily bitcoin address. If he posted an altcoin address and he can signed I think that could be enough.
Oh really? I'm not into altcoins so I didn't knew about that, but 99% of the users here prefer signing a message with a bitcoin address when selling or proving ownership of the account.
Anyways it would be a good alternative in case he posted one altcoin address and never posted a bitcoin address.
Yes a good alternative way to prove. But if he nevrr post bitcoin addrerss and this account os solely for selling purpose and he never post altcoin address. What should he do?
Nothing. There are some buyers that buy such account without any provided signed messages and it's fine with them but most likely with a lower price, but in OP's case , there's someone who is willing to buy the account for sale with the asking price of OP
Unfortunately, I don't have any posted signed messages at all 
Is there another way to show I am the owner of the account?
All posts are in English
I don't think I ever posted in Local
Okay fine I'm ready to buy only if I see the account at least ! How do you want me to pay you ? Btc will do right ?Is there another way to show I am the owner of the account?
All posts are in English
I don't think I ever posted in Local