Quite honestly find there is a surprisingly low abuse of rep rating on this forum.
The couple that i've seen well, the posters were pretty much asking for it at times, though as i don't have my nose to these kind of details i may not be up to date.
However i do think that repeated downrating of the same person does less service to the downrater than it does to the downrated.
Once is plenty, you make your point and then move on.
Rudeness and abuse need to be sanctioned in some way other than by the occasional " PURLEEEZ lets all be nice to each other guys
" interventions (
)
Personally i'd never downrate but some people can get really hurt and they need some means of closure, although i doubt that most take notice of rep ratings or even see it's there.
Keep it above the belt and no one will get downratings.