But what if person that signs it, lies about it? It shouldn't be hard to use tor, new wallet, and that's all. So why signed messages are so trusted?
I don't get it, he lies about it? Lies about what, that he signed? It doesn't matter man.
Signing message is proof that you control specific bitcoin address. U can't fake it, u can't lie about it, because its easy to verify if its true or not. Simple as that.
This scum that pretended to be satoshi lately, tricked gavin with words. There was no proof in that case.