I suppose I'm being tough when I call it "dishonesty" rather than "optimism," or an honest disagreement of opinion on how to judge the condition of used books. Someone like me isn't going to buy a book listed as "good" unless I'm desperate, but I will always buy one claimed to be "very good." I'm sure those who sell books on Amazon for fun and profit know about people like me.
Recently I bought 2 used books from 2 different vendors on the Amazon marketplace. Both books were described as "very good." But when I received them and looked them over, the pages of both were yellow. And on one of them, blotches were on the top, side and bottom edges.
These books were not "very good" but simply "good," average copies at best. So I've lost the trust I had in marketplace vendors and their descriptions since they keep overstating the condition of their books. I've yet to receive a book whose condition was understated. With digital books, I have no such worries. No yellow, brittle pages, splotches, underlining, highlighting and other things that greatly diminish my enjoyment of a used book.
Buying a book sight unseen is always a gamble, especially if you are the kind of person like me who hates poor copies that have been handled roughly and with no concern about the resale value. I never highlighted any books of my own because to me it depreciated it in my own eyes, regardless of the resale value. A highlighted book is a maimed book, like an injured animal that's lost an arm or a leg. Whatever value or necessity I would have in highlighting passages is outweighed by the diminished physical attractiveness of the copy.
Some readers seem oblivious to all these considerations that destroy my enjoyment of a book. They blithely underline passages with no thought about the long-term value of the book, They mark it up apparently because they are students and need to remember those passages as important for their future exams or papers yet to be written.
A better idea seems to me those multicolored bookmarks that can be taped to each significant page. That page can be referred to easily while not permanently marring the book. And later, the bookmarks can be removed, leaving a pristine copy for yourself or others. But...so many people are not seeing it my way.