As a librarian, it's because it damages the books. It makes the pages easy to tear. Also, depending on how they folded in it, it can put a large line through the text that makes it awkward to read. I highly suggest not dog-earing borrowed books.
In saying that, do whatever you want with your own books. They're yours to enjoy.
megan5912 t1_iueqryt wrote
Reply to why do people get mad over dog-earing books? by Sliver_wolf_1999
As a librarian, it's because it damages the books. It makes the pages easy to tear. Also, depending on how they folded in it, it can put a large line through the text that makes it awkward to read. I highly suggest not dog-earing borrowed books.
In saying that, do whatever you want with your own books. They're yours to enjoy.