Open Thunar and set your view as a detailed list. There's a nice border around the TreeView (the main part of the window), which clearly separates the column headings and the scrollable region from the rest of the window. Squeeze implements a similar look-and-feel (at least when viewed with certain settings), but does not use a similar border. I think this border would give Squeeze a cleaner look and make it more consistent with Thunar.