I think lemmynsfw stopped people who weren't subscribed to a community from voting in it (because their communities for gay people were getting a lot of downvotes from All). If that's what you mean. I think it was a hack rather than a setting though (my info might be out of date)
Yeah, that's along the lines of what I'm asking about, albeit instead of a subscription check more like, I think, however the instances disabling/removing downvoting have done so, but adjusting the scope strictly to the Local or All views.
Another approach to addressing outsider/passive voting behaviors.
I don't think that would be possible. The API is only sending "post_id" and "score" for votes, so the backend has no info on what feed a user used to send it. An instance could modify their official frontend to hide the ability to downvote from Local and All but they couldn't do anything about people using different frontends (e.g. all the various phone apps)
It’s definitely an interesting and relevant idea I think! A major flaw here is the lack of ability for communities to establish themselves as discrete spaces desperate from the doomscrolling crowd.
A problem with the fediverse on the whole IMO, as community building is IMO what it should be focusing on.
Generally decentralisation makes things like this difficult, AFAIU. Lemmy has things like private and local only communities in the works that will get you there. But then discovery becomes a problem which probably requires some additional features too.