[rdtsc]

I see two reasons:

1) If people agree with the idea they'll probably just nod their head, or upvote. If they disagree it is more likely they'll post something rather than just downvote (people feel the need to explain perhaps why they downvoted)

2) Geeks feel the need to say something contrarian to show how smart they are. It is a way to tell everyone they have a bigger intellectual penis than everyone else.

[sanderjd]

I honestly think (1) is the real key. I constantly decide not to submit comments when it turns out I've used a bunch of words to just say "I agree", and hit the upvote button instead.

Also, to another of your parent's gripes - if someone only responds to a narrow point, it should be safe to assume they agree with the other, or broader, points, and that's why they didn't respond to those.

But silent agreement and loud disagreement does make it seem like everyone is mad at each other all the time.

[benjamincburns]

Regarding #1, wow. That's a pretty remarkable insight.

Everyone thinks of the karma/reputation feedback mechanism in terms of how it promotes civil discourse, but in this case it's fairly remarkable to think of how it could be biasing the conversation toward a negative tone. Maybe it's usually civil negativity, but it's negative nonetheless. I can see how people would tire of this eventually.

I wonder if there'd be a simple way of limiting the bias? Slashdot's modpoint classes comes to mind, but then that opens a whole host of other problems...

[jader201]

#1 is why I think HN should show up vote counts to the non-authors. I think the tone of HN would seem less negative if we could see how many people actually agreed with the comment everyone else is arguing against.

It may make #2 worse though. People love to argue against the majority, especially geeks, especially on the internet.

[jonahx]

This seems about right, but I'd venture it's 80% 2) and 20% 1).

[philangist]

I have to disagree. I think it's 80% 1) and 20% 2)