For the sake of this thread: He does not sound Serious at all, not even remotely, which would rule out SLI easily. He sounds Passionate to me, end of story. And I am not the only one who thinks so. You guys have developed a personal bias for his type being a certain way etc. because you are "close" with him... I don't.
His lack of delving deeply into personal topics seems mostly E7-related. They often don't like to talk about personal topics. They often evade them. Likely in order to evade negative feelings. @
Tearsofaclown does the same thing. I almost never see him discuss personal issues, he always only focuses on ideas, concepts, information, in a very Ne-Te loop manner.
The way that Satan's Fi comes out, is whenever he takes note of who likes whom; who has a crush on whom, who is flirting with whom; he checks and mostly accurately picks up on that, and frequently comments on that, which is rather Fi and/or SX ime.
The topics he likes to talk about are simply Sp/Sx + Si, which make him seem more ST than he really is.
What you think could be Se lead is just his Se Role + contraflow + Sx, at least imo.
When it comes down to it, he lacks legit force.
