So let’s take this actual example: There’s !canada@lemmy.ml and !canada@lemmy.ca. They talk about the same thing, but are treated by the current federation implementation as separate instances.
How would you feel if there was a moderation feature to import another federated instance’s community into your own, so that the posts from the other instance automatically show up in the same feed? That way, you only have to subscribe to one community on one instance, but you get content from multiple instances. I’m not talking about crossposting or mirroring/duplicating posts between communities, only displaying the posts from another instance the community’s home server federates with, with moderator discretion.
The simplest way to allow users to merge communities like this as they please, as opposed to having the moderators choose for them what communities will merge or having the communities auto-merge, or adding the topic umbrella over communities (which I think is an interesting idea), is to allow ”multi-communities” (like multireddits), so https://lemmy.ml/c/startrek+startrek@lemmygrad_ml+startrek@mywebsite_com would display all the community’s posts on one page.
Edit: To expand on how I see @Gwynne@lemmy.ml 's topic umbrella idea, each community would have a mandatory topic (not category, those already exist), that would by default be the same as the community’s name (but could be edited), and going to https://instance.tld/t/startrek would display posts from all the startrek communities on all instances.
I understand this is an advanced federation feature, so I don’t expect it made soon, I’m sure the devs have their hands full already, just an idea.