I see karma on posts fluctuating (in particular going down) more than I would expect coming from other vote-based websites. Is downvoting really used here for posts that are not spam or trolling? Or do people just change their minds a lot?
The FAQ has: We encourage people to vote such that upvote means “I want to see more of this” and downvote means “I want to see less of this.” But I guess I’m surprised if people actually behave that way? And that some posts are controversial enough to receive active downvotes vs passive ignoring.
Gotcha. FYI I wrote and published the comment within the first 5 minutes of waking up this morning, a time in which I write my thoughts more starkly than normal. Not that it's a bad thing.
Even now, I still feel a 'push away strongly' feeling, toward the level of focus on others you suggesting with sentences like "I want/don't want this to be seen by others" and "vote up/down the things you want other people to read/not read". So let me write down a bunch of ways I think about what to vote on that seem different to that.
A lot of the time, I ask myself what incentive this will have on the person whose content I'm voting on, and from time to time I also consider second order effects on what norms others will infer.
I, too, regularly upvote stuff that I (a) disagree with and (b) am not personally interested in reading, because I want to reward people for that content because it will improve my experience of the site. For the former, many posts that are doing real thinking and give me data even though I don't form the same conclusions as the author; for the latter, lots of comments doing valuable legwork, like math proofs or data collection, or providing a reference people will want in the future.
I also downvote stuff that I agree with if it seems super aggressive or it seems like the person is wasting a lot of space/time for readers (like if they found the site yesterday and today they've written a low-effort bad-grammar confused post).
Reflecting more, I do also consider how much visibility a post will get, especially if it's in the 5-20 space and I can strong upvote it by +9 to a much stronger visibility. I guess, as we knew all along, karma is a thing that does many things, and the thing you're talking about is one of them, but I think it's misleading to imagine it should be the only one.