They
are just dots.
That being said, the only times I will negative rep is when
1. I am particularly frustrated with a spambot
2. Someone posts something, not just a opinion I disagree with, or a simple incorrect fact, but something blatantly disrespectful, like a personal attack,
and then posts again refusing to apologise. Take this thread for example. I only negative repped after the second post. In general, I also only do this when multiple posts have appeared suggesting that I am far from alone in my impression that the post is hugely disrespectful.
I've both recieved and given positive reps for anything from a simple joke to a long thought-out analysis of something, even if we disagree on the matter, such as mentor-student build.
I haven't yet recieved any negative rep here (then again, I've only been actively posting here for about a year and a half). I got one on another forum for posting in a word association game thread, with the message "forumgames sux." The truth is, many people are just too quick in pushing that "add to reputation" button. Sometimes I wish that CDs software would tell us this before, rather than after adding reputation.