My main fear with this patch is that "unquote" will become seen as
unreliable, because naive software trying to parse URLs will encounter
uses of percent-encoding where the encoded octets are not in fact UTF-8
bytes.  They're just some set of bytes.  A secondary concern is that it
will invisibly produce invalid data, because it decodes some
non-UTF-8-encoded string that happens to only use UTF-8-valid sequences
as the wrong string value.

Now, I have to confess that I don't know how common these use cases are
in actual URL usage.  It would be nice if there was some organization
that had a large collection of URLs, and could provide a test set we
could run a scanner over :-).

As a workaround, though, I've sent a message off to Larry Masinter to
ask about this case.  He's one of the authors of the URI spec.