I don't know more of account changing hands but just as crwth said, there should be a welcome note or something that says " is been long all this while" or using their regular posting format and worlds that they like using while posting as i believe everyone here has their own perfect ways of posting.
That's just how I view it if you are an active member of the forum or something. Idk. Probably hacked or sold?
The only way to know if actually was sold account is to ask owner to sign a message with address he used within 2016 or 2017 I tried to view the profile using Ninjastic.space and i find out the wallet used since and that is only wallet it filtered out. So who knows if he still has access to wallet.