PM can be used for one to one RP that can't be intercepted (I.E SMS) how ever we prefer not to, do remember that you can get sued even for PMs you sent to others if you take it in to RP (What teddy said was related to people RPing drug deals in PM to avoid court cases, he didn't mean that he wants people to RP in PM.)
PM, GM, or other methods can NOT be used in order to avoid someone hearing what you do (I.E calling for backup when others are around.)
So to clarify, if you wish to do one on one comm without anyone around you we dont really mind, but if you use it as a method to avoid others from knowing what you do, even though what you do is supposed to be RP you will be punished.