On Wednesday, 07 July, 2010 @ 05:43 zulu, Joel Rees scribed:
Okay, the digest listing does give us the message-ID line from the headers, so it shouldn't be too hard to maintain threading with a little extra copy/paste. If your MUA doesn't provide a way to set arbitrary headers, though, that won't work after all.
The digest should include all the messages as attachments, and replying to the opened message should put its message-ID in the "In-Reply-To:" header so threading works correctly (in IMAP or in the web-archived version).
I learned that not long ago in this very mailing list, by the way. :-)