What's chat message vs post? Chat message has 'root'?
Greeeeaaat question!
Been thinking about this problem a lot and what I'd prefer myself is:
1. You can only post chat messages to 1 group
2. But you can publish posts, articles, wikis, docs, books, git problems, etc... in multiple groups at once
3. You can determine per group what you get notified about on your home screen

Since I'm giving every category an emoji-icon in the group's menu, I can reuse these as a compact way of displaying the telegram-like counters in the home screen.

4. The home screen let's you open feeds by content category (posts, articles, ...).
https://cdn.satellite.earth/3d53d9393a6369940a33938ab9880971a078447153a56ee0c0f10860bf6e82a3.mov
Discussion
https://github.com/nostr-protocol/nips/blob/master/29.md
It's the two examples given in the NIP so far.
(though, I don't really get yet why it's not just kind 1's for post for example)
But as far as I'm concenrned it's a different use case.
Chat = "Gm frens", chronological chaotic feed, fun and giggles
Post / Thread = "Here's my thought I'd like to have an more depth conversation around)
Thanks, that nip is enormous, need to think it through