Shoot, I used to dogear my comic books when I was a kid. Then, of course, I was bit by the insane collector virus most of my high school years... bags and boards and double copies and all that nonsense.
Thank god that didn't last.
Lifehack Your Books: Dogear, Writing In Books, and Apologizing to Librarians-- The Glass is Too Big - J Wynia:
"I personally believe that there is no greater respect that can be shown a book than by using it.
The first taboo I think everyone should just plain get over is the taboo of writing in books. I write in most of my books. Notes about the content, things the content reminds me of, etc. When you just plain write in the margins, inside the cover, etc. there’s no way the notes for that content will get lost. They’ll forever be attached to the text they refer to.
The second is the folded over page corner (dogear). I know some of you just tuned me out as a heretic, but I dogear pages. Worse than that, I dogear for 2 different purposes. I use the top right corner of the right page as my bookmark."