It appears that shawn's archiving problems all originate from the processing of multipart/alternative messages in pipermail.

For reference, please have a look at

http://digitiy.com/posts/list1.mbox/list1.mbox

and the corresponding message

http://digitiy.com/posts/list1/2002-November/000000.html

I would suggest that pipermail looks for a text-plain part in the message, and tries to render that into HTML, ignoring all other parts.

Regards, Martin