The only useful system left on the forum is the flag system. Never seen it abused.
The Flag system gets abused a lot, but it doesn't stick. I guess it was designed to avoid the flaws in the feedback system.
I'm close to agreeing with Igebotz, although I wouldn't say that the flag system has never been abused. There have been attempts, but mostly every unjustified flag ends up as inactive.
As far as I have noticed, most wrong flags come from not understanding how the flag system works.