Comment 2 for bug 1001100

Confirmed. As far as I know, the bright line is part of the launcher itself. It is designed to brighten what's behind it (the wallpaper).

We could either remove this 1-pixel-wide line, or just change the underlying X window to ensure maximized applications overlap the bright line by 1 pixel.

It sounds like the latter is planned, but be warned that doing so could cause a regression in desktop performance, as the maximized window would be damaging the launcher region, triggering slow and expensive redraws.

The safer solution is to just remove the bright border from the launcher.