Things That Baffle Me, part three million and six

I’ve just spent over an hour bashing away at HSBC’s online banking registration service, trying to figure out why it won’t accept my name as a username, and instead keeps telling me “you must use alphanumeric characters in your username”. What’s not alphanumeric about a collection of lowercase letters?

Two questions.

Firstly, why on earth does my username have to have a digit in it?

Secondly, if my username does have to have a digit in it, why doesn’t it say that anywhere on the page?

I switched to HSBC to escape from idiotic, broken online banking systems (cough cough). This is not a promising start.