Just looking at this post as an example, on lemmy.world show it has 29 comments, but when i open it, there are now only 3 or 4. I replied to one comment, the user i replied to got banned, and the whole comment tree is gone from lemmy.world. Other instances still show all comments, including those from the banned user and my reply. I think it’s very confusing when a single post appears with different comments on different instances, and have no idea how this works.
Edit: why am i forced to upload a photo for a new post?
Well, the different "instances" are different websites, each hosting and serving their own copy of the original post and comments. You're interacting with your local copy, and your comments are forwarded along to the original website. The original website then sends out copies of your comment to all the other websites that have requested updates.
If your website has banned someone, it will reject content from that user. That's what being banned means: I refuse to host your posts. Just because your posts are being routed through a 3rd party doesn't mean I want to host them.
Like, if you got banned from Reddit, they wouldn't let you post there, either. If you commented on a mirror of a post, hosted on a different website, you wouldn't expect that comment to show up on Resdit, would you? Well, that's what the fediverse is: a network of content mirrors. Yes, they're mirrors that, generally, tey to synchronize with each other, but they're still mirrors. And independent mirrors at that.
They will never be perfectly synchronized. There's no true Lemmy to reflect. No whole. There is only what is locally hosted.
Thanks for the explanations. So a single post can have different comments showing up on different instances. So when selecting an instance, not only do we need to consider what other instances they defederated from, we also need to consider their policies on banning users and removing comments. Great. And people wonder why the average person isn’t embracing the fediverse.
Same as before: you have to take that into consideration only if you want. Probably you never cared at all when you signed to a new app in big corporation and just gave away all your data but now that there are options suddenly everyone cares and it's annoying.
This are important topics, it was time to take them seriously. This is precisely why federation is important - the instances and users can moderate, it's not a single organism that has absolute control over eveything.
Referencing Matrix when he says "why do my eyes hurt" just after waking from Matrix... It's the same here: we will all get use to have more freedom of choice, now it seems more complicated because we never had that freedom and never worried about a lot of topics that are important.