In pen and paper, the Diplomacy skill, which is the equivalent of Persuade, can't be used to influence PCs. If I play a charming character, I attempt to play charming to the best of my ability whenever I talk to PCs. I believe the reaction of the PCs should be determined by their player, however, regardless of the dice. That makes the use of the NWN skill consistent with the use of the pen and paper skill, and that makes me happy. Apart from that, all I can do is appreciate the players who humor my attempts to be charming and play along.
In pen and paper, the skill can be used to influence NPCs, however. I believe the dice should be used by the DMs to determine the reaction of NPCs, but I don't know if that's the policy here. A DM would have to comment.