In article <09cbecda-324d-eb4d-bd45-fb4e64c71a72@ix.netcom.com> you write:

That's the real danger of understanding UA as "blind acceptance" vs. 
universal support for well-behaved (if non-native) identifiers. 
"Well-behaved" almost has to become more narrowly defined than the 
"anything goes" or "any PVALID goes" from E-mail or domain name standards.

Quite right.  I wish I know where the bad idea came from that you're
supposed to accept every technically valid but illegible and
misleading IDN or e-mail address.  It's never been true with ASCII
addresses and it's even less true with IDNs and UTF-8 mailboxes.

How do we make sure that UA doesn't become synonymous with "uncritical acceptance"?

A./