it was funny seeing this right below the comment saying "I _love_ buying a used book and finding a previous reader's notes in the margins. It's the greatest.".

different strokes. if you want to ensure you don't get sick from a line being crossed out, buy new.

I have a book (not authored by Edison) that Thomas Edison scribbled his comments in the margin and I was quite happy to read them! Changing my own nearly-religious belief to never write in a book,I found that it totally changed my experience with the book and the author. There are thousands of copies of any particular modern book and it's no longer my task to preserve that unique copy for after the apocalypse. I would like to imagine my children one day being able to see their father's thoughts and dialogue with authors.