It would be even more reasonable for the original composing agent to do
line splitting for 78 characters _before_ doing the RFC 2047 encoding
I don't see how that helps. you're just going to get irregular line
breaks. and the sending agent isn't really any better at wrapping
for presentation than the receiving agent.
I've generally found it useful for the receiving MUA to rewrap anyway,
in order to hide the brain damage generated by some mailers. e.g.
From: "'john(_dot_)galt(_at_)example(_dot_)com'"
<john(_dot_)galt(_at_)example(_dot_)com>
my MUA looks at each address in the header, removes the parts that
are redundant, decodes 2047, and rewraps the results to make them
presentable (putting the phrase and the address on the same line)
OTOH, I dislike displaying agents that tinker with what was received.
Sometime people have good reasons to use long headers (long URLs for
example), and it is not up to displaying agents to second guess the user's
intent.
in general theory I agree, in this specific instance of practice I disagree.
I certainly don't like things that break lines in the middle of URLs.
But refolding a structured field seems okay as long as you don't
fold in the middle of an atom or quoted string, and refolding an
unstructured field also seems okay if you only fold at white space.
people who put unencoded white space inside URLs deserve to lose anyway.
Keith