I play on console so I don't have access to mods (yet?!) So I have no idea if there is a chest way to check hidden traits in the game.
Part of me wishes that some of these traits wouldn't be removed when the Sim moves in and becomes playable because it would add some more personality to the Sims such as the roommate ones from EP8 or the NPC Careers.
But at the same time I have a Sim who refuses to change out of her current outfit no matter what is happening to her. If she bathes or showers she does it in clothes. She doesn't change to go jogging or to sleep. She swims in her current outfit. I haven't had the weather change yet so I don't know if Cold/Snow will force her into her cold weather outfit or not. She must have some kind of trait that prevents her from changing clothes right?