Yikes!
Stains on a psa6 ...outrageous! That would be like giving an 8 to a trimmed card........oops.......never mind.
Seriously though, shouldn't all cards be graded to the same standards? As far as "acceptable"...that is personal taste. I for one would never be interested in a stained card, trimmed card, card with paper loss, card with a mark on it, holes in a card or creases that "break" the paper fibers. A mild wrinkle or soft corners are okay with me (if the price is right). As far as grading goes PSA is all over the place. I don't trust em. SGC seems a little more consistent but I bustem all out anyway. aloha, dave.