I would assume it's needed for hostname validation. Is one hostname equivalent to another? Does this wildcard match this hostname? EDIT: I looked it up. It is

I would assume it's needed for hostname validation. Is one hostname equivalent to another? Does this wildcard match this hostname? EDIT: I looked it up. It is used to implement RFC 8398 (Internationalized Email Addresses in X.509 Certificates) https://www.rfc-editor.org/rfc/rfc8398#section-5 https://www.rfc-editor.org/rfc/rfc8398#section-5