How could you tell if someone is ISFP ,or INFP in 'real' life?

@PlasticRenaissance
I can tend to tell the difference based on the aux Se and Tert Si contrast. I lived for 20 years with INTPs who also have Tertiary Si. I would describe tertiary Si as very sensitive to certain sensory stimulus, and having a kind of hyperfocus vs. obliviousness about sensory things. There are certain details that are internalized and for which the person has a sensitivity to keep it consistent. Then there are other areas where the person is completely oblivious. The person I live with now is likely an INFP (possibly ENFP), and he is very sensitive to keeping the floor vacuumed and certain aspects of his things very ordered, but then he is completely oblivious to the bathroom. Tertiary Si causes pockets of sensitivity, rigidity, and expectation about sensory experience, but it can be a little bit masked by the pockets of obliviousness that seem more go-with-the-flow.

Aux-Se tends to be more wholistically flexible about sensory experience. There is more of a generalized awareness and adaptability. There also tends to be some logic to the preferences and distastes about sensory experience - the Se-Te pairing creates a sort of objectivity that takes each thing for what it is instead of having an internalized model of it. For example, I tend to keep all my stuff relatively organized, but nothing is extremely well-kept. Everything is clean and organized enough to be easy to access, but never done to any extreme that would also waste my time.

In a way I would say that Tert-Si also has a bit more anxiety about concrete, sensory experience because of the sensitivities and pockets of blindness. The inconsistency is rooted in a kind of personal investment that can be hit or miss. Aux-Se feels a little more command of the concrete realm and is more comfortable adapting and going with the flow and changing things up as needed.

I don't know if this applies across the board, but another personal anecdote has to do with how one deals with personal, emotional pain, since both INFP and ISFP are Fi doms and share that same quality. And yes I know Fi isn't emotion, but I'm talking about making sense out of the pain in life which requires making sense of its morality and meaning and where to put it inside your own head and sense of self and reality.

When I'm overwhelmed with painful situations, my iNtuitive friends and family almost always give me a book to read to fix it. I KNOW there are important ideas in the book, but it really falls flat for me. To sit in a corner and look at tiny words in a book when I'm distressed really makes me anxious. I don't read a lot for pleasure and relaxing and I tend to feel guilty about it because I understand why reading is noble and wonderful. I have been required to read a lot and have advanced degrees, but it somehow stresses me out - especially when I'm processing complex, negative emotions.

What I need to process overwhelm is to go on a long nature walk. The energy required to move my body takes away from the negative emotional energy and provides a little relief. I could go all Forest Gump on his endless walk when I'm in enough pain. It has also helped me the times I've gone to metal concerts at small clubs because there is another kind of sensory overwhelm and a feeling that something is telling the truth, so I'm not alone in my emotion. Nature also overwhelms me because the colors, air, temperature, sound, and feeling are all very intense to me. Bad sensory overwhelm like in a megastore has the opposite effect and makes me feel really sick, but meaningful, intense, beautiful or horrific - but still aesthetic, are what I require to survive intense emotional processing. I'm not very skilled at dance, but it would be the ideal outlet for me to integrate emotion and exhaustive physical expression.