Actually, pg has stated that the downvote arrows mean the latter.
PG posted that comment five years ago; reflexive downvoting just wasn't a problem then like it is now[1], so I'd be interested in hearing if he's still got the same opinion - it wouldn't change mine, though.
[1] It's easy to look at the past through rose colored glasses, but that's not what I'm doing in this case. I actually think most of HN has improved with its new size. Niche areas are more likely to have discussions between experts, there are more people like Grellas who write lengthy and insightful commentary, a significant number of startups get successfully launched on HN, and we still managed to do all that without making too many of the original core users leave. That said, get off my lawn.
Edit: Now you're being downvoted. This is ridiculous.
Also, there are more important things to consider than an OCD-fueled (yes, this affects me, too) obsession with UI symmetry, like overall discussion quality.
Informative - I agree, but you may be full of shit
Interesting - I agree, stick it to those other guys
Funny - I agree, either schadenfreude or grits
Idealistically, humans would only vote based on content quality and not their personal opinions. But Slashdot is certainly the counter example on why this doesn't actually work
So "Insightful" as an "I agree, completely" on something that is not insightful may be metamoderated out.
It's basically impossible to do that if the value is only "+1".
But they shouldn't do this either. Personally, I try to downvote--or at least not upvote--comments which I agree with but which add nothing to the discussion. (I'm sure I'm far from consistent, of course.)
I mean, the functional use of votes is to organize the comments page. It just makes zero sense to organize the page based on the average opinion of the community rather than constructiveness/usefulness of the comments.
PG is wrong here.
At the very least, if someone down-votes they should reply as to why they disagree. There a great sense of loss when you say something factual and relevant and get down-voted without explanation.
When I've brought these issues up in the past, the conversation usually resolves with "don't worry about karma." And, I don't, but it does change the community, and about that I worry.
Basically, the community will turn into whatever is rewarded. If you reward hive-mindedness, that's what you'll get. If you reward interesting discourse, that's what you'll get.
It turns a downvote from 'I disagree' to 'I disagree and everybody else you should too'. You have to be willing to risk your own karma to take away somebody else's.
For instance the way HN works now afaik, somebody could post 'me too' comments to get enough karma to downvote, then turn around, downvote all posts supporting some idea they dislike, and there would be no way for other posters to correct this or know it was happening.
FYI, I think that this is supposed to be automatically detected and nullified by the website software, although I can't speak to the details.
Does anyone actually believes this is the approach we should be taking?