In response to my own input above: Pidgin, GIMP and other windows *do* keep descending, just like Victor and Chris had originally reported for Nautilus. Plus, the windows seem to move to the right by the width of the decoration border, too; this should be a good clue to the developers.
Also: while turning off decorations apparently keeps the windows in place (quite obvious, though), different window placing strategies (smart, cascade, random -- as configured in the Place plugin) all exhibit this behavior. Likely to have something to do with reporting the window geometry to the session manager when it's being closed.
In response to my own input above: Pidgin, GIMP and other windows *do* keep descending, just like Victor and Chris had originally reported for Nautilus. Plus, the windows seem to move to the right by the width of the decoration border, too; this should be a good clue to the developers.
Also: while turning off decorations apparently keeps the windows in place (quite obvious, though), different window placing strategies (smart, cascade, random -- as configured in the Place plugin) all exhibit this behavior. Likely to have something to do with reporting the window geometry to the session manager when it's being closed.