Yeah i was originally against it but having a custom reply kind for every note variant is also kind of annoying

it's not. the internet siloed around use cases because each platform wanted to own the data. if I follow you and you are having a discussion around a book's quote, I of course want to see that and be able to follow along and participate in the conversation. This didn't happen before due to a technological and financial limitation, but the UX of being able to discover a new book in my twitter feed because you are having a discussion on Goodreads, or Amazon, would have been kickass. Siloing kinds reduces the network effects of nostr, and means that each use case pretty much must bootstrap a large part of it's own network effects. NIP-31 + NIP-89 make this discoverable, functional and contextual at an O(1) cost for developers.