Originally Posted by
bocastephen
Not sure about Delta's written policy, but Continental states in their 'extra seat' terms that it's the customer's responsibility to ensure their extra seat is not taken by another passenger - that means informing the GA and FA that you have an extra seat purchased for yourself (so they don't accidentally put a standby there), and preventing a passenger from plunking themselves down in one of your seats.
You get boarding passes for both seats and they are both scanned before boarding. So to the GA, the seats are occupied. As far as the FA, I would put the BP stuck in the seat in front so she could see that it was indeed not available.
I have done this many times and haven't had much of a problem.