To answer your question I have no dust behind my D200 or D300s screen and no visible "wipe marks"
I hope I did not confuse you with my mention of my plastic stress experiment using the clip on protector as the object?
My comments about the lcd stress pattern relate to the actual lcd screen and has nothing to do with the clip on protector.
Your problem is a little like my feeling after I bought a new lcd tv then noticed a single stuck red pixel. That was 6 months ago and althought the red pixel is still there I no do not notice it at all.