From the
Delta website:
When you notify us that you have a peanut allergy, we’ll refrain from serving peanuts and peanut products onboard your flight. We'll also advise cabin service to board additional non-peanut snacks, which will allow our flight attendants to serve these snack items to everyone within this area. Gate agents will be notified in case you'd like to pre-board and cleanse the immediate seating area. Unfortunately we still can't guarantee that the flight will be completely peanut-free. Note that some snack products on board may be processed in plants which also process peanut products.
If you need to make us aware of a peanut allergy for an upcoming flight, please visit My Trips or call Delta reservations at 1-800-221-1212.
So unless they haven't updated their website, they do serve peanuts on flights with no noted peanut allergies.
That policy seems a bit ambiguous, though - will they 'refrain from serving peanuts onboard your flight' or will they just serve peanut free snack items to 'everyone within this area'? What is this area? (It used to be just the rows/seats around an allergic passenger)