Here's where my mind goes with all of this, and perhaps its a bit off base but, I'll use an iceberg as an analogy.
Consider that we only see 1/8th of an iceberg from the surface. The rest we can't see, admittedly there is much we don't know going on below the surface of everyone. But even though its only 1/8th of the picture, that fraction tells us a story all its own.
This gets interesting when we think of it in terms of identity. In our minds how, how we view ourselves determines much of what we allow the world to see of us.
Am I content, real, capable, beautiful, etc? All these questions we to some degree wonder about. But the world sees the 1/8th.
So out of that 1/8th, there is a portion we feel we can steer, control or manipulate to our favor. If I paint a smile on top of my iceberg does that make it a happy ice berg?
Here is where it gets tricky, to what am I seeking validation from? The internal voice of our mother, telling us how to dress? A guy or girl we once dated, and long after breaking up, we still subconsciously take into consideration all the advice and opinions they had for us? It is a matter of fitting in, not being seen as behind or noticeably different? It is a matter of expressing our personality and individuality? What if we don't know how we are supposed to feel about all of this so we simply follow the societal standards?
I cannot deduce ^THIS^ just by looking at someone else. But, if I think about it, I can know why I look the way I do.
Because we are all human, my empathy would lead me to believe that there is a sort of idea that we are appealing to when we dress or appear a certain way. Whether the target is tangible or intangible, it is completely subjective. It is known only to us, and barely, our motivations for being as we are.
Yet it is out of these understandings that we glean information about each other. In the same way that I know touching an electric fence will hurt me, and therefore hurt someone else to the same degree. We learn about each other, through our own experiences and observations of other people's behavior.
Which if this is true one way, it can also be true in another way. If I see someone else getting hurt by something, I can assume to myself that it was painful.
Because I can only see 1/8th of what is going on and out of that 1/8th a person can only do so much, I can take how much investment, economy, time, energy, effort, etc a person put into maintaining their sense of who they are to themselves, as being proportionate to how content and balanced a person is unto themselves. So regardless of who or why, the end result, and the effort required to achieve it, don't necessarily tell the whole story about someone, but it tells me enough about the relationship a person has with their idea of who they think they are, to themselves especially.