I am a player in a group with a DM who does not fully understand the rules of the system. Also in this group is a player who, so far as I can tell, is consistently breaking the rules, and giving other players bad advice which results in them doing the same.
This situation presents a number of problems for me, for the following reasons:
This is a group I began the campaign with, but had to leave and come back in later. The trouble player joined while I was away, and in total, has been part of the game longer than I have.
I have a history with this player, and other members of the group know this. In short, it is known that I have a reason to distrust anything he says.
He's not directly benefiting himself with his actions. Each instance of him breaking the rules has resulted in a boon for the other players, and not himself. Anything from giving other players bad advice about the rules which don't function as he says they do, to him granting other players bonuses he shouldn't be able to.
I'm not certain he's doing this on purpose. In each instance, a poor understanding of the rules could result in these problems. In which case, the problem is less that he's cheating, and more that he has a horrible understanding of the rules system, but believes he has a very good understanding of it.
My question is; How should I handle this kind of situation?
I'm not the DM, but the DM doesn't know what he's doing is wrong. I could tell the DM, but others might see it as me being mean to someone I don't like very well. I could confront him, but my history with him assures me that he will not listen to me. Mostly, though, my biggest road block is that 'fixing' the trouble he's caused would really only hinder the other players, and not actually help anyone, except maybe the DM who's struggling to find appropriate encounters.
I enjoy playing in this group. The primary reason I'm in the group is because it's available. However, it also contains people I find enjoyable to game with, as well as taking place in a generally friendly atmosphere that promotes good gamer etiquette.