Deprecating grandfathered tags redux

[Phillips, Addison]

> 
> 3. i-default
> 
> Mark suggested deprecating this with a P-V of "en-idefault". John strongly
> opposed deprecating this tag at all, saying that the only users of it are unlikely
> to switch to something else.

I also oppose deprecating this one for the reasons John cites. There is already text in the RFC about this item. To wit, in Section 4.1 it says:

--

   7.  The grandfathered tag "i-default" (Default Language) was
       originally registered according to [RFC1766] to meet the needs of
       [RFC2277].  It is not used to indicate a specific language, but
       rather to identify the condition or content used where the
       language preferences of the user cannot be established.  It
       SHOULD NOT be used except as a means of labeling the default
       content for applications or protocols that require default
       language content to be labeled with that specific tag.  It MAY
       also be used by an application or protocol to identify when the
       default language content is being returned.
--

We could, I suppose, add a comment explaining where this came from (probably by referring to Section 4.1). But we shouldn't torture ourselves trying to make all of the grandfathered tags deprecated. Implementations are still required to deal with them and presumably their use is rare and should become rarer as users discover the richer non-grandfathered tags. The only benefit deprecation conveys is that it, presuming there is a P-V, it tells you what you can replace the grandfathered tag with.

Addison