I'm all for rewarding the cooperative, socially constructive players but this is ridiculous.
Why not just go with the classic "community awards" where people can vote who their favourite player in a match was, end of the month the results are tallied and the winner gets some bonus stuff. As for the bad apples? I think getting kicked/voted off a server is a fair penalty: be a dick you'll get kicked, change and you can stick around.
Also, how will this identify players who are "nice" in one game but "mean" in another? I generally try to be cooperative and a team player but in games like TF2 I can't help but get agitated and go aggro on occasion.
Aside from that it just feels like Gabe is trying to set laws for politness.. In reality there's no law against being an asshole; Karma takes care of it instead. In the game world I don't see why it has to be enforced.