@xena311I'm wondering if it's by design, so that it brings a little mystery to the target sim. One way to find out (I had this happen last night), is to, for example, compliment or hug a sim and watch their reaction to it. Or try deep conversation/small talk. You'll get the green plus or the red minus sign afterwards. In my case, I forgot that another sim I had made didn't like compliments, and lo and behold, my active sim gave her a compliment and the red minus sign popped up, lol.
The only issue with this, I think, is that it won't show up on the profile of the target sim in your relationship panel afterwards. So you'd likely have to do what you'd do with friends in real life: make note of your friends that (again, an example) aren't huggers! (It's a struggle for me with the couple people in my life who don't like physical affection, because if we're friends, I'm likely gonna want to give you a big squeeze, haha.)
Of course, if enough players think it should be discoverable through the pie menu, I'm sure the sims team will talk about it.
PS gave you a like, though, because it is a great observation!
I'd understand that if it was a hidden trait, but you can easily view it for Sims you're actively playing in the moment. So I'm not sure why it can't be found out or viewed on the Sim profile for other Sims. Ideally we would be able to discover organically via interactions as well since I always like that better than having to directly ask, but you don't really discover if it's their favorite thing. You can discover if they like mischief or comedy of course since those are classed as activities/skills but not necessarily what kind of those interactions they like.
