Comment 5 for bug 133133

I just tried this and realized it is implemented in a totally flawed way: it
started nautilus(!), actually forcing a Gnome desktop on top of my KDE desktop.
This is an odd and bad idea: FF does have a built-in way to show local
directories with the file:/// protocol. The nautilus program or Gnome might not
even be installed on the system FF is running on.

FF should not rely on external programs to do that and if it supports that as an
additional option, it should allow the user to easily which program gets started
and how.