That's not what you opened the bug about, though, according to the title.

I discussed the headers-in-things-other-than HEAD/ARTICLE, and Antoine was of the opinion that they were "supposed" to be utf-8 and that in any case using surrogate escape was good enough in context.  (Headers could also, of course, be MIME transfer encoded, but in that case the header decode will turn them into the correct unicode, assuming they were encoded correctly).

Perhaps this design decision needs to be revisited, but if so you'll need a different example of a problem, and so I think this ticket should remain closed and you should open a new one.

Two new ones, actually, since AUTHINFO is yet a different problem.  And given that the standard you quote specifies bytes without an encoding, there may be *no* solution that works (that is, the standard appears to be broken, since most people expect to be able to use text strings for passwords).