There were some pretty accurate reports of this problem in the thread mentioned in the original post (#1) supported by convincing screenshots of MaemoPad+ suggesting reduced sensitivity mostly along the right edge. Regardless of the results of this poll, the problem does exist.

I've just got back my 770 from warranty replacement of its screen but as a "side-effect" the screw covers got marked and the bottom plastic panel is broken. I'll think twice before letting a technician touch my N800...