It looks like in the "install-sudoers" script that is packaged with the XI tarball, it handles replacement of the current sudoers file with a new one that has our standard lines included. You could modify this script when you download upgrades to tell it not to do that, or at least backup your current sudoers file first so you can see what the new changes (if any) would be.
Former Nagios employee
"It is turtles. All. The. Way. Down. . . .and maybe an elephant or two."
VI VI VI - The editor of the Beast!
Come to the Dark Side.