[Json] "Generators SHOULD escape all Unicode whitespace characters"?

[Jacob Davies <[e-mail]>]

I'm curious if anyone else thinks this is worth suggesting to
implementors. There are a number of non-ASCII Unicode whitespace and
control characters that are not required to be escaped right now.

I think generators SHOULD escape them. Obviously parsers must continue
to accept them unescaped regardless. The set is fairly small and could
be enumerated in the document (it might expand in future, but this
would be a good start):

http://en.wikipedia.org/wiki/Space_(punctuation)#Spaces_in_Unicode

"Whitespace smuggling" is a mild security concern and, from
experience, can be quite hard to debug if non-0x20 spaces are not
escaped. There is a small overhead of a couple of characters in doing
so.

Everything else in JSON's text serialization uses either printing
characters, insignificant ASCII whitespace between values, or plain
spaces in strings. Of course some printing Unicode characters are
doppelgängers so perhaps people feel it is not worth worrying about
whitespace either.