I responded in another comment of yours, but I'll also respond here for the sake of visibility.
We on kbin have not developed a knee-jerk "downvote everything I disagree with" behaviour that reddit had and lemmy.world is starting to have.
I completely agree with this. From what I can tell, public voting has made people on kbin.social much more reserved with their downvotes — tending to only use them for spam, hate, off-topic, or noncontributory posts and less for just disagreement — without having the risks that come with a complete lack of downvotes (i.e., not having a quick way to give negative feedback on posts that are off-topic, noncontributory, etc.).
Not federating downvotes from much bigger instances allows us to develop our own culture here on kbin without it being buried in an avalanche from elsewhere.
This is a good point, but there are a lot of issues with not federating downvotes. Yes, not federating downvotes DOES help to emphasize the downvoting culture on kbin.social, but it also means that the downvote counter is misleading and unintuitive. New users would reasonably think that, like the upvote counter, the downvote counter represents anyone who's downvoted your post (outside of people on defederated instances). Having downvotes act like they do right now makes kbin.social less approachable and more confusing to new users.
Also, as long as we're using the same system as other instances, I don't want to push the idea that negative feedback from other instances doesn't matter. A downvote is ultimately a downvote, whether it's from kbin.social, another Kbin instance, or a Lemmy instance. The last thing I want is for the main Kbin instance — the one to which many will default — to have an exclusionary culture.
If we don't federate downvotes, I think we'd be better off just ditching downvotes entirely and instead having something more conducive to how we want instant negative feedback to be used. As I've mentioned in other comments in this thread, it'd be great to have a set of reactions people can use. "This is spam," "This is hateful," "This is off-topic", "This doesn't meaningfully contribute to the discussion," etc. would be a much better system for promoting the voting culture we want here on kbin.social. And if other instances adopt such a system, we could federate those reactions with them as well.