Description of problem
A clean, logical dialog layout helps the user to quickly understand what information is required from them. It's very important to have proper spacing between window borders, controls and separators (if used), controls alignment etc.
Steps to Reproduce
1. invoke any dialog
Incorrect controls spacing and alignment.
Correct window/dialog layout.
Look at GNOME Human Interface Guidelines 2.2   
"The flags allow the specification special dialog characteristics: make the dialog modal (gtk.DIALOG_MODAL) and destroy the dialog when the parent is destroyed (gtk.DIALOG_DESTROY_WITH_PARENT)."
I have used 'gtk.DIALOG_MODAL' in all gtk.MessageDialog.
Can you give some existing example, how it should be?
The problem is in spacings. See http://library.gnome.org/devel/hig-book/stable/design-window.html.en
And dialog should be centered on parent.
done, these changes
built for rawhide system-config-language-1.3.2-8