I don't know if this can happen of course, but when using signed message to prove that you own something else than address, i saw some people doing that. So they could lie that they own something else while they don't?
They can write whatever they want. A signed message can not proof the message itself is true, it can only show you that its still the same person you trusted 2 years ago. Well, unless that person sold the private key to the address. Its not the holy grail of establishing trust, it can just be a piece in a bigger picture.