Wow, just talked to the front desk manager myself, at the hotel where my friend is staying. She was extremely argumentative, and tried to tell me, this printed copy was just an "email notice" that the certificates were being sent and not an actual certificate. And she had been told by her credit manager not to accept these. I was very insistent that she call Hotel Property Support, and tried to explain the whole process to her. She then said she couldn't take my word for it. I told her I wasn't asking her to take my word, but to call Marriott and confirm how this should be handled. There are certainly some training issues here at individual hotels. I personally have used the printed copies here before, and this is one of my favorite hotels, I hate now that I recommended it to my friend.
Cindi