Just posting this here so that maybe somebody else searching for this problem might find a quicker answer. I couldn’t find anything via Google. Anyway…
I’m using the Mailman mailing list package in Debian Sarge (now at version 2.1.5-8sarge2). When trying to solve the problem of Mailman attaching the mailing list standard footer to HTML formatted messages, rather than putting it inline with the message, the Mailman FAQ led me to a handy MIME/HTML patch by Adrian Bye. Very cool.
When trying to apply the patch to the Debian Mailman package, the Decorate.py changes failed. The only way I could get it to patch was to replace Decorate.py with the version from the Mailman 2.1.5 source code, and then to apply the patch.
I suppose undoing a Debian update isn’t the best thing one could do, but it didn’t break anything, and having the standard footer placed inline for HTML messages, rather than in an attachment, is pretty important IMO.