Are you sure about the other question? I havent seen it but 2nd person singular, formal should be same for sir and madam!
What am I missing in this discussion? Both esperE (esperAR) and escribA (escribIR) are correct forms of subjuntivo presente for ella/él/usted right?
Is this a command or not? If it is a command then shouldn't it be espera because you are addressing a señor? DL is usually pretty consistent about this.