I’ve asked the devs about it before. They completely saw the potential value in it but admitted that it would be a lot of work and so isn’t a priority at the moment.
From what I’ve gathered, working with ActivityPub is a pain in the ass. Doing so with a statically/strongly typed programming language seems to only add to the pain so going with Rust may be substantially slowing them down compared to those working in Ruby and PhP (as Mastodon and kbin do). So I believe them that it would be a lot of work.
As for kbin, I’m not sure how they got user based federation going but IME I’ve always found it to be a bit weird and concluded that it is mostly sucking up microblog content to fill up the magazines (which is a cool idea in itself). I’ve spoken to the kbin dev about it and they it is working properly if you know which page to go to but it still didn’t seem quite right to me. So though I could be wrong I’m not sure kbin has proper microblogging or user based federation just yet.
With friendica, well that’s a product of Mike Macgirvin who is basically the fediverse’s old unsung hero that appears to be making better things but without any interest in pushing their popularity … point being that it’s no surprise that friendica (or Hubzilla or Streams, his other works) has something the rest of the fediverse should.
A lemmy fork has been spoken about for a while but I’ve not seen anyone willing and able take the idea seriously. Not sure it would change the core devs approach though, they seem pretty happy doing what they want to do.
The thing with forks, or at least unfriendly/hard forks, is that they probably damage the fediverse more than help it. By my estimate the first line on the fediverse’s tombstone will be “failed to cooperate well”. I suspect there’s way too much of a “hacker … I’ll do it my own way with blackjack and hookers” culture and less of a “lets build together” culture, where the former tickles personal needs and gripes and itches while the latter requires making compromises for the greater good. IE: If someone is capable of developing user based federation on top of lemmy then they should probably think about how they can pull that into the mainline code base before starting their own prideful fork. Just my two cents.