Kind 1111 is the new comment event for NIP-29. Should be merged soon.

https://github.com/nostr-protocol/nips/pull/1233

We have a NUD called NKBIP for a Nostr Knowledge Base, that also works for publishing anything hierarchical and sectionable, like a book or a magazine or audiobook, etc.

https://wikistr.com/nkbip-01*70122128273bdc07af9be7725fa5c4bc0fc146866bec38d44360dc4bc6cc18b9