I don't see this anywhere yet, so I just bring it up here. I though this would be mostly applicable for BG2EE, but as BGEE now gets NPC's with more dialog I'll just bring it up now.
Current behaviour: Lets say you play with 2 players, both controlling 1 PC and 1 NPC (or more). Now if a dialog triggers between NPC A and B and A begins asking a question to B or make a statement B replies on, the dialog breaks off suddenly. For example: Player 1 controls Minsc and player 2 controls Aerie, this makes sure that Aerie can never become Minscs witch as the dialog breaks off.
Expected behaviour: Dialog between NPC's controlled by different players does not break off, but continues as normal.