Re: [csswg-drafts] [selectors-4] Case-insensitive health warning (#13645)

The [definition from BCP47](https://www.rfc-editor.org/rfc/rfc4647.html#section-2.2) looks crisper, with a defined grammar:

> Occasionally, users will wish to select a set of language tags based
   on the presence of specific subtags.  An "extended language range"
   describes a user's language preference as an ordered sequence of
   subtags.  For example, a user might wish to select all language tags
   that contain the region subtag 'CH' (Switzerland).  Extended language
   ranges are useful for specifying a particular sequence of subtags
   that appear in the set of matching tags without having to specify all
   of the intervening subtags.

>   An extended language range can be represented by the following ABNF:

>   `extended-language-range = (1*8ALPHA / "*")`
>  `                           *("-" (1*8alphanum / "*"))`

>   The wildcard subtag '*' can occur in any position in the extended
   language range, where it matches any sequence of subtags that might
   occur in that position in a language tag.  However, wildcards outside
   the first position are ignored by Extended Filtering (see [Section](https://www.rfc-editor.org/rfc/rfc4647.html#section-3.2.2)
   [3.2.2](https://www.rfc-editor.org/rfc/rfc4647.html#section-3.2.2)).  The use or absence of one or more wildcards cannot be taken
   to imply that a certain number of subtags will appear in the matching
   set of language tags.

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Received on Thursday, 12 March 2026 18:59:14 UTC