Not so much a no no but more of a stupid thing to do if you have taken the Queens shilling me thinks. It opens you to serious shit from the royalist side of the military. And if you cannot take the incoming then do not start it.
It matters! Smooth peanut butter, when warm - but not hot as that can be bloody painful - can be quite useful.
Crunchy peanut butter can get caught in unwanted places and become a bugger of an irritant.