Hector, I don't think either of your messages present any valid argument
against 2822 checks.
1)OF COURSE unwanted email can and should be refused before the header
or body get sent where possible. I've written an I-D to make that
possible with Sieve, FYI!!!
2)I don't think most share your opinion that all email that isn't
strictly SMTP compliant can be safely refused without refusing email
wanted by the intended recipient. Your system's refusal of emails from
me for reasons I don't understand come to mind.
3)What we're doing is changing what strict SMTP compliance means*. That
can include a requirement relating to 2822 headers.
I think it's time to move on to writing a spec and working code.
*well, technically it's all claimed to be 'voluntary', but I don't think
it really will be optional down the road if you need to get your email
to be accepted, and I think that's a good think.