> Considering that most of the comments here are in response to him, his comment clearly added to the discussion.

By your criterion, how would one distinguish between someone "adding to the discussion" and a troll? Or is it your position that trolls add to the discussion, because they elicit responses?

Is this a serious question? Can you generally not tell the difference between a comment that pushes an opinion you disagree with and a comment that exists simply to push buttons? If a "troll" comment is so good that it appears to just be a legitimate comment that you disagree with, then you should probably assume that it's just a legitimate comment that you disagree with.

Downvotes are for disagreements, too.

That's a recipe for hivemind rule: downvote everything you disagree with so that only the things you agree with show up. I think there's enough of an information bubble on HN without actively trying to create one.

That just sounds like an easy way to rationalize your counterargument while avoiding being shown the error in your thinking. If a comment is worth disagreeing over, it is worth explaining why you disagree, otherwise nobody learns anything. Save your voting for the quality of the writing, not the arguments being made.

No, actually it has been discussed elsewhere in other comment threads that downvotes are used for showing disagreement, as well. I didn't come up with this myself; rather, it seems to be convention on the HN community.

If you disagree with this, please feel free to downvote this comment. This isn't reddit, or YouTube comments, where karma is some sort of aspect of prestige. It should be freely given and taken away as part of the natural discourse.

I once thought downvoting as disagreement was disapproved-of (as I would prefer), but in fact it is not: http://news.ycombinator.com/item?id=2164087

Downvoted because I disagree with you.

That's fair, and I'd expect for you to do so. Upvoted for following convention.