I like this thread.
Alright, well, the way I learned to characterize Fi, since it is so commonplace for me, is by looking at it's "devilish" antithesis, Ti.
Ti focuses on the definitions of things because vocabulary consists of models. It notices nuances between said things, because it's all about framing an argument with logical perfection, rather than framing an argument that can be consensually observed as true, which is Te's business.
Fi is about feelings, and also about images to me. Those images and how I describe them can often contradict what a Ti oriented person might argue, but they still hold personal relevancy to me. The world takes on its own breath of life, which cannot be described perfectly, but I still try. How does something emanate its own uniqueness? All objects are observably different and special.
Everything is about connotation. What something means, and how it feels to me. Every experience is not commonplace because of the images in my mind and how I categorize them.
Sometimes this results in a habit to be unique for its own sake. Just to stand out from the crowd and differentiate myself because that's how I judge things. Fe oriented people differentiate whole demographics, or social groups, on the other hand. I see that Fe users tend to want to be the friend, while Fi users want to have a friend.
I've overcome some of these obstacles. Yes, I view my own perception of things as something of a barrier because I know there are others who view things in a separate but equally functional way. Being less self aware, and more astute to the group of people has its perks, and more aware of the commonplace can be a blessing.
Sometimes I want to access other people's furnaces. I want to see their pleasures and their pains. In fact, it's the easiest way for me to communicate. I often see that Ti/Fe oriented people are deflective because they're so focused on me, or so focused on the consistency of someone's argument, or my concern for them is redirected to someone else. It makes it so difficult to help some people, and they even view me as a threat at times, like a foreign entity being attacked by antibodies. It makes me frustrated.
It makes me even more frustrated when someone's individual rights are smothered by the moral majority. I know that this is the seed of anarchy, and one aspect of anarchy is being able to exercise as much freedom as possible, which is a common aspect of fascism (from the perspective of the fascist). So I know that my inclinations have a dark side somewhere in the body of it all.
So, you could say that because Fi allows me to see the special virtues and vices of all people, especially myself, it also allows me to see that I am imperfect for that very reason.
EDIT: I notice that because Fi coins its own symbols in the images that they give off, they can allow the user to evaluate a situation. Hence, the "value" part of this function. Some people who don't experience enough to "see" reality may have flailing values. A good example would be Lex Talionis' inability to evaluate intelligence. That sort of evaluation only comes through seeing people perform in different ways under different contexts, all under the pretense of intelligence. You could tell that many of the NTJs in that thread had a subjective idea of how intelligence should work. I'm assuming this is because of how it is commonly conflated with other ideas and misconceptions, like a high I.Q., a high GPA, nerdy glasses, or whatever other stereotype they want to ascribe to it. I'm not really sure if this is more due to Fi, to Ni seeing intuitive patterns, or more to do with the information the NTJs were exposed to.
See, a person is like a sculpture. Their personality may depict the shape and mold of the person, but their experience and choices makes up their content, what kind of substance they are made of. The final product is hard to see as due to any one cause.
"What makes the sculpture look the way it does?"
"Maybe it's the shape?"
"I think it's the colored paint."
"Nah, it's the clay texture."
The truth is, it's all of those things. So a person's behavior and the person itself is somewhat of a tautology.