Good idea,
i would see it like this: if you learn to know one personylity type you can spot all others of the same type!
Would also be really helpful if personality, once discovered, was displayed in the character cards, as well as hair, eye and skin color, to identify each person more easily.
(Have suggested something similar before ie.: some mechanic that lets you see personality types.)
Thank you both for your great suggestions.
As part of the upcoming polishing update, I've added an upgrade that lets you see a girl's personality in the phone contact screen and other girl lists. I'll expand it to notify you if a new girl you meet has a personality you've already encountered (as suggested).