Fragmentation is certainly a problem if you’re looking for Reddit-style cohesive communities, how much of a problem it is remains to be seen in my opinion. The risk with trying to do things the Reddit way is that one or two large instances become dominant and you’ve just got Reddit all over again.

One potential solution that I’ve been turning over in my mind is the concept of “meta communities” - collections of smaller related communities across the fediverse that can be subscribed to and interacted with as if they were one. Users could potentially vote on a smaller community being admitted into the meta community, or there could be some other requirement. It could even be done locally by the user through a browser extension. It’s not perfect but it’s maybe something to explore.

Alternatively we just get used to more compact communities again. Let’s be honest - do we really have to know everything, all of the time?

This is a problem that is big now, but I think can also be solved with maturing the technology in the future.

Right now I have multiple accounts for multiple bubbles, but I can easily imagine some app or website that can congregate the content coming from multiple instances and choosing the appropriate account for it to post/view with.

Thus allowing one to access bubbles that have shut each other off in one central place. Unless they do it by completely blocking sign ups in which case they isolate themselves willingly and that is also good in a way to have as an option.

If I can imagine all this as a random system engineer, surely some developers with a passion for this and open source collaboration etc. can too.

These things have a way to sort themselves out with time so no point in stressing over it.

You're right on that part. Federations works great with mastodon and its communities made of individuals directly interacting with each other's accounts.

But when it comes to interacting though communities already sparsed through instances, not only it makes it hard for people to follow all these duplicates, but it theathens the very principle of federation in a certain way. Because most people will eventually subscribe to the biggest community for each subject (tech, nature, photo), which often turns out to be hosted on the biggest instances...and that is centralization once again.

A solution could be for users to gather all the communities he subscribed to, around topics. Then your feed would be a mix of these topics' groups and single /c. Twitter does that similarly with its List feature.