I generally don't unless the disagreement has another value-subtracting component (lack of substance, poor reasoning/phrasing, factual errors, unnecessary incivility.) For disagreeable but worthwhile comments, I prefer responding instead. But I recognize the value in having differences of opinion over the use of downvotes -- comments of marginal quality (which some people disagree with, and others don't find valuable enough to upvote even if they agree) will end up dropping down the page.

What value does this provide to the reader? Community groupthink is not strongly related to truth, IMHO, and provides little marginal value, because I already know what it is and it's easy to find. In fact, I wouldn't read HN if all I found was the groupthink -- I gain far more from new or challenging ideas.

EDIT: When Amy up/downvotes, it is for the benefit of Bob and other readers. Amy receives little benefit besides maybe a little emotional satisfaction. If the vote mainly was for Amy's benefit, HN wouldn't need her vote to impact anyone else's threads -- we all could have personalized, independent scores for each comment. What benefit do I, Bob, receive if Amy is just voting on what she agrees/disagrees with?

> "Community groupthink is not strongly related to truth"

In strongly technical discussions, which are common on HN and which HN should be optimized for, "groupthink" and "correct" tend to correlate quite nicely. Whenever there is a concrete notion of "correct", it works well. It is only when "correct" becomes subjective (such as in political discussions) that shit gets messy.

In other words, downvote and upvote according to what you think those actions mean.

That doesn't mean it's a good idea. I would urge everyone (including PG) to reconsider the acceptability of this practice -- it strikes me as being harmful.

To put it a different way: PG & friends have put together a quality discussion forum. One of the reasons it remains relatively high quality is necessarily that many users of the site do not use downvotes to express disagreement.

I think the reason it's high quality is because it started as a place for the kind of people interested in startups. To me that means (statistically) well educated, ambitious, interested in STEM topics, etc...

Just like in the old days of internet news before AOL made it available to the masses. For example, sci.math had awesome discussions among leading mathematicians, and then the masses came looking for help with their homework and those guys left.

Like all good forums, if it does really well to the point that the general public takes interest, it will likely become crap.

That isn't an inevitability, it's a consequence of poor forum design. At one time, if water started leaking into your boat, it sank. Then someone had the bright idea of pumping the water out and sinking was no longer inevitable.

One mechanism that might prevent the dilution you describe is to hide low-scoring comments from low-karma users, but show them to high-ranking users. Then the high-karma users can exert influence on the low-karma users by upvoting quality comments and downvoting poor ones. It becomes a self-organizing system with a bias towards quality, rather than the open loop 'majority rules' system currently in place.

But the amount of times I've seen controversial opinions rise to the top just because they're thorough and elaborate has been really fantastic, and I make sure to upvote things I disagree on myself. On reddit, the top comment tends to be a one-liner pun -- and again, it feels wrong to me to upvote things I disagree with on Reddit, so I don't do it and it just makes the whole situation worse.

That's a weak distinction when there is a factual disagreement, since most people probably believe that factually incorrect statements are not valuable to the conversation.

I don't think this is true at all. I disagree that 1) this is a thing most people believe and 2) that incorrect statements are not valuable.

I would hope our disagreement would cause people to refine their thinking about what they post as well as what they downvote and flag.

[*] Most, referring to most HN readers

I agree.

Thing is, the "when to downvote" debate is ancient at this point and no closer to consensus.

These days, I'm given to thinking that any voting system should assume the behavior of least resistance, that it's thoughtless, reflexive and therefore only potentially valuable after being sanitized / aggregated / weighted.

Its like you invite people to a debate, where you say "please only boo when someone is saying something obscene and nasty or breaking the rules of the debate, not when they are saying something you disagree with".