The message is misformatted in the archive beacause the mail client bungled the MIME type (just "text/plain" which means "preformatted, don't reflow lines", instead of "text/plain; format=flowed" which would have been correct here).
Apple's Mail had this bug at some point as well.
edit: Seems there's more to it - the format=flowed part was also, until a 2010 release of MailMan, stripped out by the mailing list sw even if the original mail had it correctly. And then the web archiving part (Pipermail) dutifully follows the specs. Can't easily tell if this is a case of outdated MailMan installation or mail client bug. See this 2006-vintage bug: https://bugs.launchpad.net/mailman/+bug/266341
The message is misformatted in the archive beacause the mail client bungled the MIME type (just "text/plain" which means "preformatted, don't reflow lines", instead of "text/plain; format=flowed" which would have been correct here).
Apple's Mail had this bug at some point as well.
edit: Seems there's more to it - the format=flowed part was also, until a 2010 release of MailMan, stripped out by the mailing list sw even if the original mail had it correctly. And then the web archiving part (Pipermail) dutifully follows the specs. Can't easily tell if this is a case of outdated MailMan installation or mail client bug. See this 2006-vintage bug: https://bugs.launchpad.net/mailman/+bug/266341