I wish SE would have a reputation system for players because right now, there is no incentive to be good because when you do DF, the chances of you meeting that person again is nil. Anonymity is the enemy. Have an up/down vote system.

It's easy! At the end of a dungeon, you can give each player an up vote if they were awesome, a down vote if they sucked or had a bad attitude, or abstain if you can't be bothered. People of similar rep will be grouped together: good players will not see people with lots of down votes, and down votes won't hinder the experience of people with lots of up votes.

People are gonna say it can be exploited, but these are the same people that claim the sky is falling each time something cool is added. I doubt it will be exploited to a level these people are worried about.