I think the community has accepted that RFC 2822 has superseded RFC
822 for all practical purposes.
IMHO - if you're implementing a mail _reader_ you do well to rely
heavily on RFC 822. It's a much simpler, easier-to-understand, and
easier-to-implement-correctly grammar than the one in 2822, and with
very few exceptions you need to be able to understand messages written
according to the RFC 822 grammar anyway.
OTOH, if you're implementing a mail _composer_ you need to rely on 2822.
So I tend to view 2822 as augmenting 822, rather than replacing it.
The opt- productions were a nice idea, but IMHO they didn't work as well
as we hoped.
Regime change 2004 - better late than never.