My position (at the end of a longish offline thread) is that
1. Sending anything other than colon-space is stupid. I know - I used an
MTA that did it for years. People write careless perl scripts to
process mail and colon-tab or just-colon gives those scripts
indigestion.
2. Some people do it (even after careful thought) and 2822-upd is not
the kind of document that should render thoughtful, compliant
implementations non-compliant.
I'd like to see a new document that says "here's what you shouldn't do,
even though 822 and its successors have allowed it for decades, and
even though some people like to do it". (colon-space, multi-address
from, etc.) But such a document has to start at PS. 2822-upd isn't that
document.
Arnt