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Let's rephrase the question then: why did you put the seam where you put the seam? I was just a bit surprised that you included the two polygons between the lips and the philtrum in the lip part, is all.

Just at the time, looking at the mesh and deciding where to put the seam, that looked like a good place for it. That would be my first guess, based on what I know about how I go about things. There's also a possibility it was just a mistake, since the current version was done with the lo poly mesh, while the original was done with the high poly mesh.

As you may remember, UVLayout doesn't show materials. It would make things much easier if it did, to serve as reminders for such occasions where it might be better to stick with predefined material groups, but then again, it was designed mostly for Maya users, where one would typically UV first and assign materials later.