13" MBPr purchased 2013-12 Have never used anything other than damp paper towel on the screen. Have the "stain" near the camera only, so far. Nearly identical to image 14.
Given the similarity in pattern (starting near the camera along the edge) do you really think this is caused by user error? Do you think that everyone is cleaning their screen in the same wrong way in the same area of the screen?
No, I have no idea. My comment above was a tangent to the original article and only pertaining to paper towels. That's what I meant by starting my comment with "Unrelated, "