Another one is where they have a limit on how short a name can be. I even remember a discussion on the Linux kernel mailing list about that. Linus himself wouldn't accept names shorter than (IIRC) three letters. But I was in high school with a guy from another country, his name consisted of a single letter. He didn't even have a first or last name, only that letter. And it was official - when the loans and stipends arrived it was all printed on the common wall on 132-char folding paper, from the governmental student loan bank. His name (one letter) was there.

(p.s. I did present what I wrote above on said mailing list back then, but as far as I remember people simply decided to ignore it as too rare to care about, in addition to those who for some reason taught I just made it up (why should I?))