After I use mirror command, I press ctrl + E and select Mark Seam. Then, for some reason, the main head unwraps again into a deformed shape with yellow spots...
It "seams" to me that when you create a new seam the UV editor rearranges the texture to fit everything in the square. And the yellow spots are probably the indication that every vertice is selected. This also happens when Kent demonstrates the process in the video.
