This page is intended to summarize the perspective of the Knights of Noromath leadership with respect to the cognitive science surrounding "meta-gaming" in NWN.
When a player has multiple characters that are active in the campaign, often there can end up being conflicts with information possessed by the player of those multiple characters. In order to acknowledge this problematic situation, direct involvement in supported factions such as the baronies or the Temple of Mystra are limited to one Player Character at a time.
When this sort of conflict manifests in the inevitable circumstance of affecting other players, things become needlessly complicated and expectations between players can vary.
Let's start with a common example of what could be and should be avoided.
Player A has just one character. Player B has two characters, both of whom have interacted with a magical illness plot.
In a dialogue between the two players, Player B claims to wish to research a cure to the magical illness. But, Player B has already done this same roleplay on another character, and when Player A hands them over the plot item that they will need, this will trigger the item-transfer (muling) script and actually produce a rule breach that notifies the DM team.
In this situation, Player B feels that they are being set up! They believe that Player A should consider that they play multiple characters, and somehow avoid putting them in this situation. In our opinion, Player B has very unrealistic expectations for those around them. Asking Player A to take some additional consideration is unfairly impacting their immersion, enjoyment and overall experience.
The burden of avoiding crossing any plotlines rests entirely upon the player of multiple characters. It applies to many situations such as playing both a vampire and a vampire hunter; it is normal for vampire players to have alternate characters for daytime, but how absurd is it to possibly hunt for your own character?
Although playing multiple characters is not disallowed, it should be done sparingly and with care to keep everything straight.
Top-down and Bottom-up Processing
In cognitive science, it is understood that bottom-up processing is the work your brain does as information goes from the eyes to the cognitive centers in the brain. Top-down processing is the work your brain does to use your experience and your expectations to generate your perception of any particular thing. These two things are constantly working together to form your perception of reality.
Unsurprisingly, "perception makes reality" is a very old saying.
In the context of roleplay, your top-down processes are comprised of in-game and out-of-character knowledge all at once. You can't stop the integration of this information, because the brain is doing all of this automatically. So the little things you know will be preconsciously included in whatever you do, no matter how much energy you spend trying to inhibit it and second guess yourself along the way.
We're not saying to avoid playing multiple characters! What we are saying is to please be considerate of the effect that poorly handled information can have on our virtual game table. This also extends to OOC joking about "so and so being a vampire" or that "everyone's character will die" or other things that even if they are fun for a moment, bear forward unwelcome and detrimental outcomes that take away from the story we are telling.
Everyone on the Knights of Noromath has the right to experience the campaign story in an intimate and personal way, free from harassment disguised as banter.
Some links which are informative on the topic of cognitive science: