I would speak to one of the managers and ask what is the purpose of this bill and what do they expect that guests should do. Why are guests being given a bill for a zero charge, are guests expected to sign it, is this a ploy to get tips for Marriott employees, what purpose does this serve for the hotel or for guests, etc. Tell them there is a thread on FT and suggest that the manager respond to it directly or that you will be glad to post their explanation. Put management on the spot to explain.