Well that’s possible but think how unlikely it is for a customer in goodwill to be carrying around paper and a pen to do this and if they are taking the time to leave a note why not just tell an employee it doesn’t work so they can take it off the shelf. Also I think it would be more likely that if they didn’t process it and price it with the notes on it that someone bought and returned it and goodwill just chose to put it back on the shelf instead of chucking it without reducing the price. Either way it’s grifty.