Dear Mr Lang,
I am one of the people who, years ago, insisted on an ISO 639 policy
regarding 2- and 3-letter codes for languages.
The reason the rule exists is to insure stability and uniqueness in
the use of these tags on for instance the internet. Tok Pisin, Tetum,
and Palauan have the ADVANTAGE of having only one code to worry about
right now. The official language of my country, Ireland, have to
contend with two possible taggings, ga/gle and en/eng respectively.
I am not a voting member of the ISO 639 JAC, but I support their
decision. "tpi", "tet", and "pau" are unique identifiers for these
languages, and they are not disadvantaged in any way for not also
having 2-letter codes.
In my personal opinion, there is no reason that ANY more 2-letter
codes should be added.
Michael Everson * http://www.evertype.com