Hmm, it takes looking at their face, hearing the voice and a short interaction for me (I usually get a strong gut feeling either way). By that point I already know if me and the other person are going to get along long term or not or what it would take on my end to make it work. Face to face is easy, because I'm highly observant. I have an instinct for this or natural ability. I'd even assert that its very difficult to lie to me, because I'll pick up on it through the other person's tone of voice, micro expressions combined with the verbal content I'm receiving. Like a spidey sense of "the signals don't fit / this is genuine / not genuine". Sometimes ppl are so bad at faking things its cringe.
Usually ppl on the spectrum are confusing to read, because they give off confusing signals. I can instantly spot if you are gay or have some unusual mental thing going on. (the alarm bells will go off, this stuff is very obvious to me even if the person is hiding it well)
Since I pick up on all of this, it becomes easy to make slight alterations to my exterior persona (minute modifications needed stuff I must say or avoid and so on) to get along with different people without having to really & truly fake it. I can for example win the trust of even the most difficult people e_e because figuring out who they are and what they want is easy.
I guess this and my rather firm / strong subjective moral sense backed by solid logic is why I'm doubting ILE, as the type is Fi PolR after all and I'm always aware of when I'm offending quite intentionally I might add to shock ppl & push boundaries, to instigate debate & keep things moving. I could just play it safe I guess, but that's boring. Even my subconscious emote usage is geared towards making me affable.
<.< this stuff can get rather overwhelming if I'm in a larger group of unknown ppl and I have to keep track of many ppl this way.. mainly because I can't turn it off. To a certain degree this works even through texting.
EDIT:
as a guy I never had any relationships problems beyond just risking asking a girl out, I guess based on the above its obvious why.