Easier said than done UX-wise 😉 . What do you want to see when you click on a book highlight? Because let's imagine the author of the actual book is dead. You'd give priority to diplaying who actually wrote it, right? And only then show who published this version on Nostr.
Margin notes are the highest signal. If a friend lends you a book and you find highlights and scribbles from your friend on the margins, that’s where your attention will go first. It’s not just a highlight. It’s not just a book. It’s not just a thought from your friend. Is the intersection of a book you might enjoy and a person you care about.
Seems like it could also be useful for book clubs.