Books offered for sale with no mention of restoration are implied to be unrestored and complete. By offering a Bats #123 for sale, if I ship a bats #123 with a coupon cutout, the book was not what was offered and the sale has not been completed. If I ship a Bats #123 with restoration, the book was not what was offered and the sale has not been completed. When a sale is incomplete, the buyer can force the return for a full refund, even if returns are not allowed.
This is the industry standard.
If I ship a Bats #123 and the buyer disagrees with the grade, the sale has been completed and any remedy for the buyer is based on my stated terms or whatever the buyer and i can agree to, after the fact.
Anyone who wishes to have other terms should explicitly state such terms in their sales thread eg:
These books are offered "As is"
These books are offered with No restoration guarantee
I know nothing about comic books and you will be getting whatever the hell is in the picture. God help you if there are no pages within the cover, because I sure won't.
"Found these books in my attic! Please feel free to ask any questions! " would not absolve the buyer from the industry standard as far as I am concerned, unless they specifically followed it up with something like the above.