Richard,
On 2/1/2019 1:30 PM, Richard Wordingham via Unicode wrote:
Language tagging is already available in Unicode, via the tag characters
in the deprecated plane.
Recte:
1. Plane 14 is not a "deprecated plane".
2. The tag characters in Tag Character block (U+E0000..U+E007F) are not
deprecated. (They are used, for example, by UTS #51 to specify emoji tag
sequences.)
3. However, the use of U+E0001 LANGUAGE TAG and the mechanism of using
tag characters for spelling out language tags are explicitly deprecated
by the standard. See: "Deprecated Use for Language Tagging" in Section
23.9 Tag Characters.
https://www.unicode.org/versions/Unicode11.0.0/ch23.pdf#G30427
and PropList.txt:
E0001 ; Deprecated # Cf LANGUAGE TAG
As I stated earlier: language tags should use BCP 47, and belong in the
markup level, not in the plain text stream.
--Ken
