Wouldn't that require current implementations to ignore events with an `h` tag? Seems like you'd want to exclude notes belonging to a group. Of course, NIP 72 has the same problem currently.
Discussion
For public groups (communities):
Chat
👉 read + write within the community only
Everything else (including "kind 1")
👉 anyone can read anywhere + only members of the community(ies) can write
Maybe this should be made clear since I don't even know if people agree with me on it, but the difference in NIP-29 is that the relay shouldn't give all random events to anyone who walks by unless they include an "h" tag at least.