I had it in my head that it doesn't matter who blocks who, if one instance defederates from another it looks the same from both instances - you don't see new content on one from the other. Is that not the case?
If beehaw blocks lemmy.world, Lemmy.world can still get the beehaw content, but any comments made by lenny.world accounts, as an example, are not visible to beehaw users, or on the beehaw instance. At least that's how I understand it.
Not sure how it plays out if a lemmy.world user makes a comment on another instance then the beehaw user views the same 3rd server though.
It would be the case if they implemented authenticated fetch, which is a fediverse protocol that mastodon and some others support, but it's not widely enabled because anything that doesn't support it would get blocked. It basically allows servers to reject fetches from defederated servers, and since lemmy doesn't support it, defederation is somewhat one way since the defederated server can still anonymously fetch new content despite being defederated.
So I asked about this once before, and my understanding is that since beehaw defederated:
Beehaw won't accept anything new from lemmy.world
Beehaw won't send anything new to lemmy.world
So even though lemmy.world didn't block beehaw, it is still effectively cut off in all meaningful ways.
You could still see:
Beehaw and lemmy.world users interacting together in communities on instances that neither has blocked (because in this case the third instance is acting like a middleman between them)
Lemmy.world users can still post to the "phantom" beehaw communities and it will be visible to all lemmy.world subscribers, but no one else will see it since it can't reach Beehaw, and thus can't be distributed to all the other instances.
What happens to the phantom posts if they were to refederate? Does everything just suddenly mesh back together?
Like if I commented on an old Beehaw post. Would beehaw users eventually get that comment pushed to that post, in the case of federation? Or is it just lost in the cracks because it happened during a time when they weren’t accepting lemmy.world content?
My understanding is that right now Lemmy is very poor at "catching up" on missed content in general. You can see it anytime there is prolonged downtime that the same post across multiple instances gets out of sync. So most likely in the event of re-federation, as Lemmy is written today, the old content would not be received - just new content. Hopefully things are improved in the future
Just doing a quick search of the Beehaw communities I'm subscribed to (I have hope...), I found this post from 3 hours ago and this post from 2 days ago - note that both were made by lemmy.world members, and you can even see some comments on the second one from lemmy.world users too. I'm guessing this is the sort of thing you saw, going by the last point @CMahaff mentioned in their reply.
It's possible you saw a post that predated the defederation. Cached copies of those posts still exist on the lemmy.world instance. You can reply to them, but I believe that only the other lemmy.world users will be able to see it and respond.
I've been sorting by different methods and going a bunch of pages in - I'm not sure where it was or even what the post was about. It just struck me after I had paged past that I'd seen that instance. I'll watch for it again - thank you for your replies.
Edit: could a Beehaw account post here? Maybe I saw it in a username.
My understanding is that no one on that instance can see any of us on any instance.
So no, they couldn't post to lemmy.world.
They could post to somewhere we both federate too, such as lemmy.ml and we would be able to see that post, but if we respond to them, they wouldn't see our post.
Beehaw has a goal of being a completely troll-free safe place for their members. When the Reddit surge happened, .world and shit just works had open and automated signups, and apparently Beehaw communities saw a lot of harassment from people on those two instances. The mod tools don't allow them to do much more than defederate, so that's what they did. They said they intend to refederate when they have tools that allow them to deal with the situation better.
There's one part that has always been a lie perpetuated by beehaw: lemmy.world did have an email verification requirement for sign up at that time, despite what beehaw claimed.
I know this, because I made my account right at that period of time, just days before they defederated.
TLDR – Beehaw claimed it was too hard to moderate the spam coming out of Lemmy.world because Lemmy.world had open registration and were allowing Reddit levels of trolling