"mis" update review request

[Frank Ellermann]

Mark Davis wrote:

> An alternative would be to explicitly broaden the description of
> "zxx" to be "no linguistic content, or programming source code".
> That would be a compatible change to 4646bis, since it is a
> broadening.

I'd like the proposed "zxx" comment for rather different reasons:

IMO it is _not_ changing the existing "zxx" semantics in any way.

By definition BCP 47 claims to be only about human languages, and
draws the line roughly with "art".  Anything outside of this field
is considered as "zxx", and programming languages are explicitly
mentioned in BCP 47.

So if they get any language tag at all "zxx" was and is possible,
only the description is "mis"-leading when read outside of its
BCP 47 context, i.e. in the "zxx" record in the raw registry data.

Adding a comment to reenforce the intended context doesn't change
or broaden the meaning, it clarifies what "zxx" is.  Same idea as
for the proposed "mis" comment:

Comments added to subtags adopted from ISO standards or from UN
region numbers should IMO never change, restrict, or broaden the
real meaning in those sources, but they can reflect or clarify
this meaning when the description "mis"-erably fails to do this.

Frank