It could probably be done with a dedicated local client

I'm personally of the mind that we should be imagining a world where all 3 of these solutions are at play. 1 is absolutely the most important, and Admins should be taking an active role here where possible (particularly as it relates to dead community cleanup). I personally think they are the missing element needed to negotiate these sorts of consolidations. 2 and 3 on the other hand are pretty simple features and even if Lemmy never takes it on, I think it's reasonable that any one of the new fediverse link aggregators could take this up. The only other thing I'll say is multi-communities absolutely must be sharable. Ideally, it should even be possible to link multi-communities with the "!" syntax or similar.

I've heard that bluesky is attempting something like this but I'm dubious about bluesky generally. Otherwise, I think this is a killer feature of the fediverse that has really not yet materialized.

I think the actual problem here is that URL posts are linked (and combined in the feed) automatically but text posts can't be linked at all.

Check out more of these at !opencourselectures@slrpnk.net. Also can't go wrong with The Missing Semester from MIT