I'm hesitant about doing it for kind 1 because there is such a wide context, lots of notes collected over lots of relays - don't think it would really work because for the user it there is so many unrelated notes. But imagine a pool of relays focused on some content:
nostr:nevent1qvzqqqqqqypzphzv6zrv6l89kxpj4h60m5fpz2ycsrfv0c54hjcwdpxqrt8wwlqxqyghwumn8ghj7mn0wd68ytnhd9hx2tcprdmhxue69uhhg6r9vehhyetnwshxummnw3erztnrdakj7qpqcu2498m77mq80cj5tuh3l8rnw97e8vx54alva35pzmr207lt4xuqqz5htc
Even if you group across multiple relays, a user is choosing to connect to related content. A user is reading some related articles that have been embedded and so you (service provider) or the client is able to construct some sort of HNSW search, and pass some sort of subnetwork within some distance close to your note.
