That sounds really weird. I've never heard of such a thing in Korea or anywhere else. A bookseller (especially those selling brand new books) should never blemish what they sell by marking it any way, because such markings instantly make it a used book. I think most people won't even accept the merchandise, just like you wouldn't accept a piece of clothing that has a magic pen scribbling on it. If it happened to me, I would complain and never go back to that store. I believe what you read about publishers refers to the printed page that contains the book's identification information, which is fine since it's just another page of the book. I don't know all the facts, but it doesn't make any sense to me. No respectable publisher or bookstore would do such a ridiculous thing.