That list of ways to filter out your evals are a bunch of great ideas, but unfortunately they don't work well when they're computer based. My undergrad school switched about halfway through my time I was there, and they noticed both a decrease in the quantity of responses (duh) and a slight decrease in average rating since you wound up with only the extremes actually filling them out.
I remember my biggest frustration the first time I TAed a class was a fellow grad student who took the class pass-fail, didn't turn in any homeworks, never showed up to TA sessions, and barely got a pass. He blamed me for poor preparation and all sorts of other things when he never even showed! (I know it's him since, well, I'm at a tiny school and TAed a class with only a handful of people, and the personal comment that was left was a bit of a giveaway.)