Perhaps I'm only acknowledging that I'm less likely to downvote someone that I agree with? For example, if someone speculates wildly but it's consistent with my own experience, I'm not likely to downvote. If someone speculates wildly and it's inconsistent with my experience, I'm far more likely to downvote.
Probably where we disagree is whether it's OK to downvote a comment that someone put effort into. I've seen someone ask a question about a particular technology, and someone who clearly has very little experience with that technology posts a long screed where they're ~~talking out their ass~~ sharing their opinion in a way that sounds authoritative. Or maybe they're repeating business-level talking points instead of getting down to technical brass tacks.
I hope that gives an idea what I mean. I don't want to see comments like that on HN, regardless of how much effort or how well-meaning the comment is.
Yeah, I like this perspective but I think there's two axes we can separate a little. One axis is disagreement. (I agree with you <-> I disagree with you). the other axis is effort / coherence. (I'm going to invest significant effort to clearly articulate my point of view <-> I'm going to make a flippant off-handed comment).
Disagreement alone isn't the problem - I've had some lovely conversations on HN with people I disagree with. Eg, a couple weeks ago I had this interesting exchange[1] talking about RMS on the FSF board. But the conversation worked because everyone was careful and articulate. When someone says something I disagree with, but they say it in a thoughtful, well articulated way, I learn something new.
There's probably more factors at play, but as a rule of thumb I suppose downvotes are in the low effort + strong disagree quadrant. In that zone I feel like there's no implied intent to even talk it through. And absent conversation, why are we even here?
[1] https://news.ycombinator.com/item?id=26611767