Here's that PR I promised:
https://github.com/nostr-protocol/nips/pull/1589

Also related:
https://github.com/nostr-protocol/nips/pull/1079

Flotilla requires nothing of relays in order to work, and very little in order to work well. Most of the changes above are just new event kinds that fit new use cases, and aren't actually core to groups.

Blog post still incoming, but please chime in on the PR if you have thoughts. 

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