I subscribe to the prevailing belief that it's the termination of that broad smudge, which is at a slightly deeper depth into the mask than the area outside the smudge perimeter, that gives rise to the C-Scar. Then the question is what is the cause or reason for the smudge? I have a theory for that which no one has mentioned here before.
The root cause I think is... wait for it... wait for it... the nose droop.
The what? Well, I don't know if there's conventional name for the feature, but I'm referring to the sharp downward angle at the tip of the nose. It reminds me of the way the nose of the Concorde angled down for landing which the designers called "nose droop".
The nose droop to me always looked like a last-minute addition to the mask, and I believe it was. There's a lot going on at the tip of the nose. Several distinct surface facets and what looks like the starting point of that smudge that swipes from just behind the nose tip across the right cheek, terminating in the area of the C-scar.
I believe the nose droop was added either as a final step in the sculpting of the mask, or to the plaster cast made of Brian's original sculpt. Because of the roughness of the features I'd guess it was to the plaster cast. It looks almost like they were scraped off. And a curved tool would logically have been used along the cheek which could be why the termination of it is also curved. But it could also have been done as part of the original sculpt and caused by a thumb swipe.
In the vicinity of that smudge on the right cheek and along top and bottom there are transitions between sections that are curved and sections that are straight. The cheek might have started out as a smooth continuous curve, but by adding the nose droop, the last part of that curve was truncated. I think the straight portions of the cheek were needed to provide transition and flow to accommodate the addition of the nose droop.
The fact that the nose droop is painted silver also contributes to my notion that this feature could have been a last-minute addition to enhance visibility by the camera. By flattening it and painting it silver the result would be an enhancement of the reflection of light back to the camera in the profile view.
Looking at the picture I mocked up, I'm suggesting that starting with the red facet is the first part of implementing the nose droop. This includes the downward angle to the nose tip and flattening to make it perpendicular to the camera in a profile view. The orange and blue facets are then needed to merge with the red facet. And the grey swoop starting at its intersection with the blue and orange facets, pressed in hard at first to connect seamlessly at that junction and pulled across the cheek with continuously lighter pressure to its termination in the area of the C-Scar.
Just a theory (but aren't they all in regard to the C-Scar). But it came to mind as I was trying to add a nose droop to my DLDPX to enhance its accuracy, and I found that to accommodate that addition I needed to change a lot more, along the lines of what I outlined here.