is there any interest in an index of known public twtxt feeds that provides a json-based api for things like a social graph, getting more complete views of a thread, etc..

It could be interesting.
As has been discussed, these services are ‘centralized’, although having mirrors hosted by volunteers syncing somehow, would be a good idea. So if one server disappears you can jump to another.

I lost track of Registries, but they seem to be down, which is an example of that problem:
https://twtxt.readthedocs.io/en/latest/user/registry.html

And I’m aware of this kind of CSVs made by ‘scraping a social graph’, but they seem to be manually updated:
https://github.com/tkanos/we-are-twtxt

@prologic@twtxt.net for sure, could be time to take some pages out of bluesky’s book, their model for how this would work is very interesting

additional apis for Yarn’s crawler would be nice. And docs for the existing ones