Trust me, it was worse before Civil Comments, if you can imagine such a thing. 

Sites are going at this problem in backwards fashion. What's the goal of people looking to game the site? Of ideologues trying to drive an agenda? Anyone looking to abuse the system is looking to a) remove posts they disagree with, and b) promote posts they agree with.  Once you acknowledge that core thrust, you design the system to make that HARDER to do. You should lean to inclusion, not exclusion, and force strict equality in commenting weight.

Why would you institute a rating system, and allow gaming to drive comments to the forefront?  Why would you institute a filtration system and allow gaming to remove posts from view? You're giving them the specific tools they want!