I have been very happy with most of what I receive.  But peoples opinions differ in what is acceptable and what isn't.  Is there a way to mark for my on personal use on a person I received books from that I would not want to order from again?

In a word, no.

You may, however, make a note of them yourself.  But it would mean cancelling and losing your place in FIFO if their names came up again.  But, seriously, PBS is a pretty big place and the odds of your requests going to the same person multiple times is pretty slim.