I explained this in my post: https://lemmy.world/post/149743
Those communities still exist on this instance, they just aren't synced. You can see new posts from only lemmy.world users. Any posts/comments you make are not shared within the wider lemmyverse.
Effectively that community is a zombie community on this instance. Just unsub from that community, it's useless to you unless behave decides to refederate.
This is where the Lemmy interface could use some work. It should definitely notify users when they are about to post to an instance that is defederated with them and let them know that no other instances will see the post.
The fact that these communities exist to instances that are cutoff from the "true" instance is a horrible UX. There should be a giant "unplugged" overlay signaling that that youre essentially writing to a google doc that is not connected to the internet.
Out of curiosity, are lemmy.world mods still able to moderate these zombie communities?
It seems odd that people would be able to post in them when the people who are supposed to handle the communities just aren't there.
This is the correct answer, lots of people think defederating is one-directional when it's not. It's 100% blocked communication both ways, meant to be the nuclear option as a last resort (sadly the lack of other moderation tools makes it a second resort after reaching out to the other instance).
If defederating still allowed any communication, it wouldn't be useful if a remote instance was malicious and exploiting protocol-level bugs and trying to exploit other instances. Defederating should protect against that too, hence 0 communication whatsoever.
The uni-directional option would be limiting a remote instance, which unfortunately isn't implemented here.
I read elsewhere that it's not completely bidirectional when it comes to posts on a third party instance. For example, if lemmy.world and beehaw.org users both post to a thread on another instance that they are both still federated with, lemmy.world users will see the beehaw.org users' posts, but not the other way around.
I haven't confirmed if this is true yet though, so maybe someone can correct me if I'm wrong.
When I say bidirectional disconnection I'm talking only about directly between the defederated instances in question since some people are suggesting that the instances are still directly sharing content in one direction. In your example the instances are still bidirectionally cut off, you're just suggesting that a third instance could relay content between them. That would be theoretically possible but I don't think it works like that currently, because that idea gets shot down in Mastodon for several reasons, including the fact that trusting content relayed to you from an intermediate server could open up the possibility of the relaying instance tampering or impersonating user accounts or faking content.
Because we didn't de-federate with them. So, if you comment, only other lemmy.world users will be able to see your comment and interact with it.
So does the rest of the Fediverse need to defederate from Beehaw to clean up their sites?
EDIT: Nevermind I can see that if that happened, we wouldn't see Beehaw users posts in other fediverse servers that both sites are still federated to. It seems like defederating is a messy thing to do.
Because Lemmy.world is still federated with beehaw. No one on beehaw will see anything you do.
As the "owner" of a community an instance is responsible for distributing posts made to it to other servers. Beehaw have said they're not listening to lemmy.world and so don't distribute posts made by lemmy.world users.
We're basically in a read-only state it seems like
(edit: but apparently there's more to it than that)
No, we are not getting any Beehaw posts from Beehaw, and nobody outside of lemmy.world can see any of the posts in question.
The only time we see any posts that say Beehaw, it's because someone from lemmy.world is trying to post there. Nobody on Beehaw, and nobody on any other instance can see them.
Go to another instance and check the Beehaw communities. Posts created from lemmy.world aren't there.
As others said. But to be more precise, someone on lemmy.world tried to post to !technology@beehaw.org. That post will get sent to BeeHaw but their server will reject it because they've blocked lemmy.world.
Other users of lemmy.world can see this post, but nobody else. That's because lemmy.world knows about the post since it's own user made it, but every other instance will be looking at BeeHaw's servers for new posts in that community.
*edit: My post below gets some things wrong. See https://lemmy.world/post/149743 by @AgentGoldfish for a better explanation. You can stop reading here unless you like partially incorrect information.
There have been several answers to this, but I don't think everything has been fully explained.
Instances are not aware of other instances by default. So, if someone creates a new #Lemmy or #Kbin server nobody will be aware of it.
Now, when a user on your new Lemmy server (CoolLemmy) starts following a community or user on another server (LemmySphere), that server becomes aware. CoolLemmy will start showing all the content from LemmySphere in its "All" feed. Also, all content from CoolLemmy starts to appear in the "All" feed on LemmySphere.
Next, when a user on CoolLemmy starts following a community on SpaceLemmy, LemmySphere will also show SpaceLemmy content in their All feed. This is how one big web of content starts growing (federating) across all of these different instances.
Sidebar (and this is an important point): let's say a CoolLemmy user posts a comment on a LemmySphere thread. What happens? Their comment, and any images, etc., are saved on CoolLemmy, not LemmySphere. Please keep this in mind if you are on a server that doesn't want NSFW content, illegal content, drug content, etc, on their server. If you think you are posting NSFW content on a NSFW Lenny instance you are actually posting it on your local server, which may get you banned.
So, let's say SpaceLemmy starts doing things that LemmySphere doesn't like. LemmySpere defederates (blocks) them. Users on SpaceLemmy will still see LemmySphere posts and comments (public content can be viewed by anyone). SpaceLemmy users can add threads and comments (which, remember, are saved on SpaceLemmy) on Communities and threads on LemmySphere, but LemmySphere is not going to show them to their users - SpaceLemmy has been blocked. SpaceLemmy users will still see them and, because CoolLemmy and SpaceLemmy are still federated, CoolLemmy is still going to see those comments and posts.
If CoolLemmy also defederates SpaceLemmy then, in this example, only SpaceLemmy users will see SpaceLemmy content.
If SpaceLemmy defederates both SphereLemmy and CoolLemmy, only then will SpaceLemmy stop showing content from those other servers.
Defederating is the equivalent of closing your eyes and putting your fingers in your ears and saying, "la la la I can't hear you" and actually meaning it.
I had an issue with a cross post like this with another post I made, but I didn’t know they defederated with us so maybe that’s why the bug is happening. I deleted the beehaw posts so hopefully that cleans up your feed? I’ll just avoid cross posting there in general.