I made a few changes to my citizen's names file and started a new game. I've got 5 citizens by turn 33 with one duplicate name (female), despite having 19 different female first names and 17 different last names. So it seems that the game is not doing as much as it can to choose unique names. I tried playing around with the <PreferenceWeight> tag, but having more than one of those within the <FlavorTextOption> threw an XML error. So I have no idea what that tag does or how to use it.
I have a slight suspicion that <PreferenceWeight> designates how often females appear to males which is great if so- Still testing.
But regarding the names, I just get weird results. Sometimes it brings up a custom name, but repeatedly the same name numbered and at times it even brings up a default name I deleted! I don`t get it.