Communities on different instances about the same topic should have the option to essentially federate so a post on one appears on all of them and opening any of them shows you the comments from all of them. This way when lemmy.world is down its not a big deal because posting to any news community federates to all of the communities instead of barely having people see your post. Federation could be decided by the community mods and the comments can have a little “/c/communityname@instance.name” on it so you know which community the comment was originally posted on.
There is one major problem with the implementation that I hope you can understand with an example. Suppose there are three forums - motorsports@example1.com, motorsports@example2.net and motorsports@example3.org, which eventually start mirroring each other by default. Let’s also suppose that a user is, for whatever reason, banned from example1.com but not from example2.net or example3.org. Should the user try to subscribe to motorsports@example2.net, must the latter honor the ban list from example1.com and ban the user as well, or should each instance have its own ban list, knowing well that users can evade bans by subscribing to another of the mirrored communities?
They can have their own ban lists and users on the instance as the banned user won’t see the same banned users posts just like how federation works now
Alright, but should the banned user be able to see posts from the banned instance if they’re cross-posted to a non-banned instance?