I'm curious, for the "deep one-on-one": is this more often with people you know well, or casual acquaintances who pique your interest on a particular subject?
For as long as I can remember, I have had a keen interest in understanding more about what I don't understand. Observing is my number one passion. Since I don't understand quite a lot, I can be easily entertained and captivated. I understand that a lot of people on News.YC want to talk about intellectual topics - I fancy myself a snob because I feel like I can listen/talk about anything (as long as the other person is interested in what they are talking about)
By "deep one-on-one", I mean conversations where I am basically allowing someone to play the role of 'expert'. Not necessarily deep philosophical topics. But something the individual is keenly interested and/or passionate about. It doesn't have to be a person I know well - I've had these fulfilling mini-conversations with people on a train (and it tends to be strangers/acquaintances because I keep a moat around myself).
For example, yesterday at our office galley I got into a 5-minute conversation about soccer (with someone who plays for fun on weekends). I learned that one of the best ways to become a better soccer dribbler (foot skills) is to practice kicking a ball in the surf on the beach (because you have the water resistance to deal with). He also said that the reason why Americans aren't good at soccer (football) among other reasons is - Americans have perfect playing fields, while Brazilians, they grow up kicking stuff in the dirt, sand so the groomed soccer field is easy compared to the rough + tumble environment they learned on. I love learning about the 'hacks' (to become better faster).