This has probably come up before but I was wondering
The only other forum site I visit is Ravelry - about knitting and crocheting. In their forums every post has buttons beneath it that say things like 'agree' 'disagree' 'interesting' educational' funny' and 'love' and then users can click on these to indicate their thoughts. They act like toggle switches - click once and it's on click again and it off. This means you can disagree with some one 10 times, just once.
I find them useful and interesting. Not only is a quick way for me to indicate 'yes, this is what I think' with out posting a full reply, they act like little voting booths so you can see what others think too.
I would say in general it's a little less emotional over there. People are less likely to get upset with others opinions then what I sometimes see here. But it does happen. I can see people getting a hurt if they get a bunch of 'disagree's, but I overall I think most would enjoy the feature.
I don't know if this is a common function on internet boards, that you have explored and rejected, or something unique to Ravelry. I'd like to see it on GS