As an adult, I don't wear shorts either. But as an 18-22 year-old I did--which is why I remember that part, I suppose. It's not like I went around in Daisy Dukes before, and I still think all my shorts were modest, even though above the knee. The whole issue just highlights the absurdity of much of that honor code.
Most of the adult women I know would probably have more of an issue with the sleevless prohibition than anything. Because heaven forbid some sex-deprived young adult should see a woman's bare upper arm.
I did go back and browse through it. It's much longer than I remembered (obviously, since I only remember one bit).
http://honorcode.byu.edu/content/view/3585/