i have 3 guesses here about the trait/personality system:
1) it let you to role play 2 characters at a time by letting them to act as you want them to and in the meanwhile not needed to make the decision for them as their trait will decide who wins in what situation.
2) in the beginning of game you are shaping the character by role playing them and decide how they argue in what situation, after reaching a certain point (untill all of the traits had its own alignment), the ai will be able to make decision based on given traits in the later game.
3) nothing role play is involved, it is just how you farm yourself some extra skills/social points.
