Wouldn't those have to be created first?

Yeah. If the API can do it, we could make a specially privileged account type or something. And yeah, good point, creating all of those users would be rough as well. Those would need some kind of prefix or suffix to avoid duplicates/collisions too.

If we could build federation into the open source reddit stack I think it would be really powerful for a bunch of reasons, but it's an uphill battle for sure.

Yep, and it sure is. I had no idea how many ancient and deprecated dependencies this codebase had until I tried to port it to Ubuntu 18. I've put at least 30 hours into that without much progress to show. It really needs a full refactor to python 3 and probably the Pyramid framework, with a lot of the guts like baseplate being torn out. It's more than I really want to do or can do with our small team. I was hoping you'd handle it or even the Lemmy guy who hates extreme content but is supposedly building a federation anyway :)