It will not accept your battle tag, if you use Æ/æ, Ø/ø or Å/å. For myself, i use æ in my name, Kælegrisen#2136. So my idea is, that we would able to use those letters. :)
OpenID is service that allows you to log-on to many different websites using a single indentity. Find out more about OpenID and how to get an OpenID enabled account.