That's cool but that's a fixed 10 cents, so basically Discover is forwarding to you some of the money they receive for handling the debit in the first place.

I have yet to see a debit card do a 1% cash back, which is really common in credit. Here in Canada, the debit charge (handled via the interbank Interac "sort of coop") are really low, 6 cents per transactions is about par. There's nowhere to tack on even a 10 cents cash back.