Personally I don't see this change being good for everything.
Let's play devil's advocate:
create table abc(U&"foo\2003" int);
U+2003 is 'EM SPACE', in Unicode's General Punctuation block.
With the current version, format('%I', attname) on this column is: "foo "
With the patched version, it produces this: foo
So the visual hint that there are more characters at the end is lost.
I can agree, so current behave can be useful in some cases, but still it is bug (inconsistency) between PostgreSQL parser and PostgreSQL escaping functions.
Currently, any multibyte char can be unescaped identifier (only apostrophes are tested). We should to test white chars too.
Regards
Pavel
Best regards, -- Daniel Vérité PostgreSQL-powered mailer: http://www.manitou-mail.org Twitter: @DanielVerite