My clearly annoyed comment a couple of days ago https://news.ycombinator.com/item?id=8135515 started out underwater a bit, flowed up to 7 and then back down to 5, which means someone's clicking downmod. I think these downmods are fine because I wasn't entirely careful in writing that post (whiskey will do that).
I tend to think of downmods just like the catcalls you hear in the House of Commons from the opposition party. It's chaotic and rude sure but that's just human nature.
I had to go back 80 days to get to a visibly downvoted comment: https://news.ycombinator.com/item?id=7733672
Which comments are downvoted for disagreement?