Here's the text of some applicable WoJs:
Jim: What [a soulgaze] shows you is /true/. But it isn’t necessarily /all/.
For instance, a ‘gaze could show you that a man was self-disciplined, sober, highly organized, dedicated to his principles, and that he loved dogs, and all of that would be /true/. But it /doesn’t/ tell you /everything/ about Adolf Hitler.
Granted, a soulgaze of Hitler would probably have given off a big vibe of either “crazy” or “ruthless” too. They tend to give you a pretty good core sample of the individual in question. However, every wizard gets things a little bit differently than any other, in terms of how the soulgaze is perceived. Not every wizard sees things in symbols and allegory, the way Harry does. There’s a whole spectrum of different “filters,” I suppose, of how the basic natures of others are perceived.
As for misinterpreting what they perceive, or putting their own preconceptions on their interpretations? Please. EVERYONE does that, wizard or not. It’s part of being human.
In reply to the question of whether a soul can change over time, my humble opinion lays thusly:
Since your soul is the essential you, anything that truly touches you will change your soul. I know that having to watch a five year old die over a period of months while I and the rest of my pedi ICU did everything we could to save him changed me. I know that meeting and falling in love (yes, and finally marrying her!) with my Lady and Wife changed me. And I know that there are more changes down the road.
I an not the person I was at twenty. Nor am I yet the pperson I will be at sixty if I should get that far. Life is an ongoing process, after all.
Jim: Ah, but is it a process of pressure and change, or is it a process of polish and refinement? One could argue that the events that “changed” you in actuality only revealed a truer facet of your soul than had previously been perceiveable–that those events only changed you inasmuch as a rough diamond is changed by a master jeweler’s tools. The diamond doesn’t become an emerald–it just becomes a more beautiful and quinessential diamond.
(Just Devil’s Advocating here, for the most part, and throwing that thought out.)
In any case, it may just be possible for a person to change enough for a soulgaze to reveal something else–but it would have to be an utterly incredible kind of change. Something along the lines of the billionaire executive who, after a near-death experience, gives all his worldly goods to charity, leaves home in his pajamas, and takes up a life of underwater basket-weaving and meditation. And even that seems a little mild to me, thinking of it.
Anyway, it’d take a truly epic change of heart and mind–to the point where you would practically *be* a whole different person, and not just a person who happens to be you with a lot more life experience to inform his outlook.
(And, in fact, there’s all sorts of theories about people who this happens to after a near-death experience, regarding “walk-in” souls who come and inhabit a person near death, changing them and becoming a kind of inner Yoda to the “native” soul.)
The third sight reveals truths about people and places that aren’t evident to the naked eye. Are the specific images that are seen intrinsic to the subject, or is there a measure of personal metaphor and interpretation on the part of the viewer? In other words… Let’s say that Wizard A grew up in America, and may consider the embodiment of evil to be a devil-like figure. Wizard B is from India, and might instead associate evil with a rakshasa. They each view a subject with their third sight. The subject is a vile and malicious person. Would this be revealed to them both in the same way, or would what each one sees be influenced by his own cultural background?
Jim: Not only would the Western-raised wizard and Eastern-raised wizard perceive things according to the cultural biases and subjective experiences, they might not even perceive them with the same /senses/.
The Third Sight is different for everyone, subjective, and inherently slanted towards ones own experiences and background. So while two wizards might look on some totally-gone, bloodthirsty warlock and see a bloodthirsty warlock, they might see it in very different ways.
Maybe Harry looks on him and sees some Hannibal-Lectery figure crouched on the floor grinning and soaked in blood. But maybe Ancient Mai looks on him and sees a bare, twisted white tree in the center of an unbroken field of white snow, representative of the individual’s loss of spirit and humanity. And maybe Rodriguez looks at him and hears some kind of hideous music that accompanies the individual and makes the hair on the back of Carlos’ neck stand up. Maybe Klaus the Toymaker looks at them and sees that his head is covered in cracks and flaws, and that underneath the parts where the flesh looks chipped away, something rotten and horrible is underneath. Maybe Listens-to-Wind looks on the warlock and smells something rotted and vile.
It’s way different for each wizard, and it’s why even though soulgazes and third sight can be used as evidence in, for example, warlock trials, there is also room for argument and interpretation–that’s how Ebenezar defended Dresden, for example. He claimed that he Saw more than just “murdering warlock.”
Plus, it isn’t flawless. I mean, if a wizard looks at someone who has just suffered some kind of horrible physical or emotional injury, he gets a much different picture of that person than if he sees them a week sooner, or a year later. If a wizard looks on someone who is in a towering rage at the moment, it’s going to have an effect on what is Seen. Maybe not an enormous effect, true, but at times even a little bit of difference in shading can change the overall picture. Oh, plus if the /Wizard/ is in a radically altered state of mind, it can shade things differently, too.
Ultimately, the Sight is something that is best relied upon for making one’s own decisions, for supporting one’s intuitions and observations–as long as one remembers that while it is always true, it isn’t always completely correct. Circumstance can, at tmes, effect what is Seen.
What all this seems to amount to is that if Prime!Harry soulgazes Mirror!Harry, he will see his own soul,
but with different facets highlighted/revealed, and with a potentially different shading. He'll definitely see something that's quintessentially
him, but probably with the soul equivalent of different clothes and makeup, and probably some different scars.