Comment 7 for bug 308446

Not strictly linux but probably a GTK+/X11 thing. Windows uses ported GTK+ libraries that don't need X11 whereas on linux and osx platforms gtk-based applications run under X11 (on osx I have the 'Dialogs on top' options included in the 'Windows' preferences tab as well). But I didn't dig into the sources to see what causes this platform dependent difference. (ping @theAdib - do you know why?)