RE: RFC 2617: Which character should be used?

I think the spec could say that UTF-8 SHOULD be used, but private
agreeements are allowed.

However, be aware that according to 2617 and 2616 respectively
1)
      password    = *TEXT
2) 

   The TEXT rule is only used for descriptive field contents and values
   that are not intended to be interpreted by the message parser. Words
   of *TEXT MAY contain characters from character sets other than ISO-
   8859-1 [22] only when encoded according to the rules of RFC 2047
   [14].

       TEXT           = <any OCTET except CTLs,
                        but including LWS>

I don't know if this causes problems or not.