Should we update an RFC if people refuse to implement parts of it ?

I've been doing some EAI tests.  RFC 6531 section 3.7.3 says that domain 
names in trace headers SHOULD all be U-labels.  In practice, everyone uses 
A-labels for reasons that are not absurd.  The FROM clause has the name 
from the EHLO command which has to be sent as A-labels, and it's quite 
plausible to have a message where the message itself is entirely ASCII, 
sent to a UTF-8 address, which then could be forwarded to an ASCII address 
except that it has those U-labels in the trace header which would have to 
be downgraded.  I've talked to a couple of MTA maintainers who have told 
me forget it, that's silly, not doing that.

In a situation like this, would it make sense in a future update to the 
RFC to adjust the advice to the reality?

Regards,
John Levine, [email protected], Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly