All of my comments in this thread started with negative points from down votes then stabilised. It seems that whenever there's a controversial topic, there are a few people who down vote every comment that goes against their viewpoint.
I've had the impression that people who have the ability to down vote are reasonable and well-respected in the community, so it kind of surprises me that these things happen. Maybe down voting just seems lofty to me because I'm not karmic enough to have it.
It's also funny that I talked about being downvoted, and am now a little above 0 afterward, oops. I figured the thread was dying down and I'd respond before it was abandoned completely.
Getting enough karma to downvote doesn't really mean that much, it just means you've been here long enough and maybe submitted a few articles that got on the front page (it's much easier to get karma by submitting articles).
