Was reading the post about names... My girlfriend has a family name with two letters. In Asia, it's common enough so it's not an issue but in Europe there are some systems that refuse my girlfriend's name because it's too short.
I remember hearing from a classmate of mine in college that 'O' is a legitimate Korean surname. Blew my mind! And what about people without a surname? Mononyms are common in some parts of the world, like my native state in South India.
Her first name has two parts, so she just combines the first part of her first name with her last name. It's incorrect but still matches more or less what she has on her password.
It's kind of frustrating.