Comment 26 for bug 194472

#24 and #25 are spot on. As a relatively new-to-linux user, this is what I would expect and understand. One additional consideration might be to display the "explanation" message (#3, et al) AFTER 2 or 3 failed sudo attempts, or after 15 seconds, etc. This will likely cut down on the confusion while not making overt changes to the sudo "interface" for experienced users.
If an explanatory message is included, I would further propose that it includes the location of the combobox to change the star behavior.