Neither do I. And I created that link.

Edit: huh that's weird, I could access it before.

It's actually a link to a comment in this post, for some reason jerboa gave me a kbin link. I've removiing the kbin part. And reformatting it

Edit: ok so I need to work out how to translate these links coz that didn't work

Essentially it was about the fediverse using a "push" model, meaning instances push their comments to other instances. It means you can see the community and posts, but if you comment on it, it won't get pushed to the instance that hosts the community - only people from your instance will see the comments and posts

If a community defederates, it essentially blocks the push, preventing it from reaching the community.