Option c seems far and away the best. The reason I browse certain communities over others comes down to admin moderation. Certain instances have stricter admin control and seek to influence political dialogue one way or another. I just don’t want to get banned again for posting the word “tankie” when it’s entirely relevant to the discussion at hand.

I don't think it's a huge issue, there were often multiple communities for the same thing on reddit

I personally don't think this is a huge issue, but it is an issue. I usually pick the biggest community on a topic, or if there are multiple that are fairly active, subscribe to both/all. The only real complaint I have about it is that users will often make the same post to both communities, so I see duplicate posts on my timeline and the discussion is split in half.

I do think it would be nice if there was a way for community mods to choose to combine two communities across instances, in a way that they would appear as a single community to users. I don't know how that would be implemented though.

The real problem is how do we centralize all communities. I mean, there's a Linux community on lemmy.world, but also Linux Web sites, forums, chat rooms, people on Twitter that post about Linux. Sometimes people talk about Linux in emails, or text messages. They're probably having in person conversations about Linux. This fragmentation is ruining things.

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.