When you view any content on Lemmy, you are viewing and interacting with the local copy on your local instance.

Federation means that your instances’s local copy should be up to date. Any changes or comments made on your local instance will be sent to the host’s instance, to update the master copy there, which is then sent out all other instances.

Defederation cuts this off, leaving users only able to interact with their instance’s local copy.

Posts are public. Any instance can download posts, so when Lemmy.world asks beehaw for new posts, it gets them so you can see all of beehaw’s posts, and get your content.

Beehaw defederated with Lemmy.world, so beehaw is no longer requesting updated posts from Lemmy.world. So beehaw users will see increasingly out of date local versions of Lemmy.world communities if they try to view them.

Defederation also means that beehaw blocks anything that requires two-way communication, such as comments and votes. This is why beehaw will have mostly empty comment sections on Lemmy.world.

If you post or comment on a beehaw community, that interaction will not be federated. Beehaw will not get it, beehaw will not add it to the master copy.

But Lemmy.world added your content to its local copy. Other lemmy.world users will see it, but no one else. Even an instance in full federation with both, because instances only get updates from the master copy on the community’s host. And defedrration means you cannot update the host’s copy of the community.

This behavior is weird and confusing and not user friendly. I think future versions should treat one way defederated communities as unavailable or read only. Content that is out of date without explanation, or comments that go nowhere without an user-facing error message is not good ux.