The good news is this was fixed in latest https://codeberg.org/Kbin/kbin-core/issues/1019 the bad news is it hasn't made it to kbin.social yet so hopefully whenever this instance is updated it will be fixed
It looks like all the spam I've seen are from newly registered accounts. Perhaps this is something you've already considered, but would shutting off registration on kbin.social and pointing people to other instances until things are more manageable help?
You filed the issue on it! xD
I remember this happening before so it might be the same thing, auto media preview basically: https://kbin.social/m/kbinMeta/t/77143
The issue is here https://codeberg.org/Kbin/kbin-core/issues/1019. It was fixed with a PR but I don't believe that PR has made it to kbin.social yet
I certainly wasn't trying to counter your post in any way or anything (especially as a non-kbin.social user), just provide information for people who might not be aware. kbin.social users basically have to see all of their posts with no way to interact or exchange with the other party, giving them little options. And for people who are unaware of this, they might be replying to their users in hopes of discussion or debate that will never happen
My guess would be it's due to you having a follower from kbin.social https://kbin.social/u/@cwagner@lemmy.cwagner.me/followers
This is anecdotal, but I don't experience these log outs on fedia (I have to relog like once every few days but that doesn't bother me, I assumed it was cookie expiry but maybe it has to do with server restarts or something). So I can understand if it happens more often to kbin social users it might be some other way it's set up like caching or something that others might not be running. Then again, without version info, it makes it a bit tough to debug so this might not be helpful, fedia could be running some random sha atm which might be the reason.
I had a look and did not find an issue about receiving notifications from blocked users. I might've missed it, but feel free to add one https://codeberg.org/Kbin/kbin-core/issues or I can add one for you
Regarding messaging instance admins, there is a contact link in the footer, but I have no idea what it does or if it works. Perhaps there needs to be an issue to streamline that process as well (interestingly my instance links a mastodon and email contact, kbin. socials is a bit vague with no information)
On the sidebar, if you click the fediverse icon (the 3 dots with lines between them), you can turn federation off. This will show you only local content. However, this does still show local kbin users posting to federated magazines, because technically they're posting to the local copy on kbin and it just happens to get federated out on the backend. But it should reduce the amount of completely federated things you see
It was verified and fixed, so users on kbin. social should at least be able to see their posts now https://kbin.social/m/kbinMeta/t/173366/lemmy-ml-is-no-longer-shadowbanning-kbin
I don't know of every instance of course, but from the general purpose ones the order of up-to-date from most to least at the time of posting would be something like: kbin.run, fedia.io, kbin.cafe, artemis.camp (specific API branch), kbin.social.
But there's also other considerations. fedia has a double post/comment issue and a low amount of 500s. Artemis has been giving me a lot of 500s, can't upvote anymore (just reloads the page), commenting doesn't always federate. Many instance admins seem to have disappeared since 3 months ago. I'm not sure what life is like on instances I'm not actively using so there might be issues unknown to me.
Edit: the keys that I look for are localization / ui changes. "more" dropdown now has "more from domain" on updated instances. The UI for the sidebar is different, and most recently the footer is differently styled. There's also the federation list of instances page in the footer now.