Charles Lindsey wrote:
The occurrence in a Netnews article of a
Return-Path containing non-ASCII within a comment is as unlikely as they
come.
You have completely missed the point. That point is that your
"heuristic" is inherently unworkable. Any scheme that requires
encoding content via standard (e.g RFC 2047, 2231, 2396) methods
for header fields requires that the syntax of the header field
be known. That will not be true for uny experimental header
under the currently-proposed Usefor draft scheme, which requires
gateways to encode untagged utf-8. The issue is not, and never
has been, whether or not any particular header with specific
content might or might not appear in a news article.