scarus, you are dead right, but then, we are still talking about requiring you to have played a game against someone to give them feedback, and theoretically, if someone has played you 100 times, they have the right to give you feedback 100 times...if you are dishonest 1 time, then why would it be a bad thing if you get the 99 other good feedbacks to show your true character. (this applies to Jota's revenge positivity comment too)
As for a verification of grievances...that would require hundreds of person-hours, especially as the site grows. Perhaps a solution would be a drop-down list of options (suspected secret alliance, backstabber, rude, insulted my hair, etc) to limit the stupid "he/she wasted my time" comments. The other possible deterrent which could be added would be to have the option to "view all comments left by this person" So If I said "Lack is a doody-head" and I knew you could track down all of my comments and see how immature I was being, then it might dissuade me from posting them.
Then there are all sorts of back end stuff we could code for the mod(s), like user "flagging" of grievences which are stupid etc. so that it is easier/less time consuming for a mod to track these down. or perhaps "grievance weights" (similar to theose "did you find this review helpful - yes/no" check boxes) so that you, as users, could make stupid grievances go away (of course, we run into the same problem scarus pointed out earlier with populairty contests, especially with clans on the rise)
Anyhoo, just some thoughts
Twill