I hate people who quit out of Team Slayer. I hate people on the other team when they quit out of Team SWAT. I love it when people quit on my team in Team SWAT though, because it's easier to go 1 on 4 in SWAT then slayer. Honestly, I don't mind the whole quit ban system, but they could improve on it by making it distinguishable between lag and actually quitting. And quit banning began in Halo 3 because people were using the quit button to create booster accounts. I am not sure why it is in Reach, except to discourage trolls.
As far as AFKers go, I wish they would be perma-banned. Or at least rank reset/month long ban from x-box live, not just Halo Reach MM. People who cheat should face very dire consequences. AFKing is cheating, which is why it is punishable.
As far as the OT goes, in my opinion, if you get people who constantly quit you should just avoid them. That way, you will not see them in MM again. Halo Reach is a game, and people quit games sometimes. If it's happening too often, try a different playlist. Otherwise, stop being a baby.