@AbyssalMonkey
You don't get it do you? The reason everyone at the bar were astonished/frightened was because he was able to revert a very old wound, as well as revert back hair from the old man when he was in his prime.
That would basically mean if he feels like it, he could return you to an infant at his current power right now.
That's the specific reason the other guy is trying to restrict his actions by enrolling him into his guild, this power is just too broken. And there's an even worse fact is they have no idea whether he can even restore himself if he dies( from a surprise attack) so that would basically mean he's immortal.
That fight where he reverted the guy's skill points, he did that just to not attract too much attention. Had he wanted to it would have been a worse fate to the guy.