Davem, thanks for the reminder that not all we read today was originally printed. Still, when it was included it was within JRRT's lifetime, so he must not have seen the possibility of spoilers as a disadvantage.
Bęthberry, excellent thoughts! There were, of course, murder mystery writers back in Tolkien's day, so I assume the authors and readers of 'whodunits' must have been interested in keeping others from knowing the murderer, but your remarks on the non-existent role of spoiler warnings in traditional literature are a valuable addition to this discussion. And you make an interesting connection between novels and novelty!
Legate, I enjoyed your post about your personal reading experience. I find it fascinating to see how differently the same book is perceived by different people - and even by the same person at different times of her/his life.