hierarchy in language tags

[Sean M. Burke]

As I was looking over old messages, I saw Jon Hanna writing, on at 10:54 AM 
2002-12-06 +0000:
>[...]In particular recognising Old Irish in Ogham as a form of Old Irish
>would require guesswork on the part of a system built currently (guesswork
>based on treating language tags as hierarchical, which previous threads have
>shown to be ill-advised).

Can you point to where that was shown to be ill-advised?

--
Sean M. Burke    http://search.cpan.org/~sburke/