I'm genuinely stuck. The Matrix S2S spec seems effectively unimplementable in its current state, with core functionality being undefined, which leaves me with only a few options:
1. Try to implement it anyway, and be chasing undefined behaviour and broken rooms for the next 5 years
2. Try to get all the holes in the spec resolved, which will probably take a decade at this pace, if it ever succeeds at all (and will burn me out, guaranteed)
3. Fork the protocol into something that's actually strictly specified, but this will fragment the ecosystem because of missing compatibility
4. Just give up on implementing a Matrix server. Take the (extremely rare for me) decision to just abandon this project entirely.
All of these options suck. I see no remaining solutions until the Matrix core/spec developers actually start prioritizing fixing the spec over other things.
Now what the hell do I do?
Well. I've just learned a couple of things about the #Matrix spec and its process that are giving me serious concerns about the long term.
I'm refraining from sharing details here right now, because they would be extremely easy to misinterpret, and it's not an immediate problem to worry about.
However, I do think that it's time to start seriously thinking about forking the protocol, and I've created a room for talking about this: #fork:pixie.town
If you're interested in working on this (as a developer, as a technical writer, as a spec designer, or something else), then please join the room!
However, it's important to recognize that such a spec fork will impact many existing communities and developers, and so breaking compatibility is not to be taken lightly. If possible, it should be avoided.
So if you feel like burning everything down and starting over, this is probably not the project for you. Also, I do expect everybody *not* to harass Matrix core folks over this.
If those things are not an issue for you, then please join! 
@ch0ccyra1n I was hoping not to have to add a "don't talk to me about XMPP" comment to my post, but...
Yeah, no interest in relitigating the topic of XMPP because those discussions always end the same way and it's never constructive
@joepie91 oh that's fair. Sorry for asking
@joepie91 why not just use XMPP?