If the notes are good it can be a gem. If not, then it also really bothers me.
Another way of saying it is discussing a book with some people will be really rewarding. But others you will rather prefer not to. This is just an instance of a more generalizable rule: people develop preferences regarding who they want to spend their time with.
FWIW, I switched over to the post-it note method (mostly) in the 90s for real live books. Grab a few colors and shapes. Easy to remove if you don't want to share your thoughts with someone else if the book is something you later choose to get rid of.
Another way of saying it is discussing a book with some people will be really rewarding. But others you will rather prefer not to. This is just an instance of a more generalizable rule: people develop preferences regarding who they want to spend their time with.