We ran into a recent issue in my group where one of the PCs attempted to persuade another. The character who was being persuaded mentioned something about how persuading another PC is not allowed. I, being unclear on the ruling, asked them to wait on a verdict until I had a clear answer, as neither could find any evidence that it was allowed or not. Is this allowed? If so, how can I stop it from being escalated? Knowing the player, he will get mad about being persuaded, and will likely pull some sort of stunt along the lines of, "I'll make a persuasion check to make you give me X" over and over again to prove that it shouldn't be allowed. Is there a way to avoid this?