Oh wow, thanks will do. Queued!
https://youtu.be/JSauiX7XHDo?t=1066
This is worth watching, your exact issue. From 17:45 on lexicons, but whole video good.
Discussion
nostr:naddr1qvzqqqr4gupzqprpljlvcnpnw3pejvkkhrc3y6wvmd7vjuad0fg2ud3dky66gaxaqqgxymr4v4ekk7fdweej6mn0wd68y94g600
And this for context on the "facets" thing they have, which works alongside.
These facets are clean, until you have to interop on them.
The concept of interop is different. You can't "riff" on stuff there over there (purposefully). Either you jump on an existing bandwagon, or you start your own, nothing in between.
Basically what's happening now with the same NIP 29 group as viewed in 0xchat and Chachi—hard to see how that could happen on ATproto. There would be a lexicon clash before you even get to the rest of it all.