Before heading overseas, I sat through a bunch of the standard Army Afghanistan 101-style cultural briefs.
Don't gesture with your left hand. Check.
Don't expose the soles of your feet. Roger.
Don't ask about female members of the family. Check-raj.
And remember, an 'Afghan' is a person from Afghanistan, where as an 'afghani' is a unit of currency. Don't confuse the two, or you'll come across as just another ignorant American.
The first three I knew from Iraq (though it might surprise you how little police and soldiers there care about those rules, or how often they violated those rules themselves), but the last one I hadn't heard before, so I stayed careful to remember it.
Then when I got here, I heard a few people point out in a thou-shalt-not sort of style after hearing someone call a person from here an 'Afghani' that it was culturally insensitive, and wrong.
Except here's the funny part -- I started to notice that when the people from here referred to other fellow countrymen, while speaking English, they used "Afghans" and "Afghanis" interchangeably when referring to other people from here.
In fact, I heard it enough times that I had to just start asking them, every chance I got. As it turns out, the distinction isn't really something they think about, or care about. Yes, the currency unit is the afghani. As for the people, every Kabuli (yes, that's the term!) that I speak with tells me the same thing -- it just doesn't matter.
So I have to laugh a little at the idea that people putting together some of the basic Army cultural training are far enough removed from the culture itself to be emphasizing stuff that just, well, isn't so.