I think I know why : bugs go to darcs-devel, and darcs-devel is set to make you
reply to darcs-user (because it's meant for automated traffic only).  Ideally,
it should just be reply to bugs@darcs.net for these messages.

Adjusting the title. We discussed this on #darcs. To repeat, currently we have
bugtracker traffic going to darcs-devel, but that list sets reply-to to
darcs-user. I think there are two things wrong with this: first, email
discussion of bugs gets split across two lists unless people make an extra
effort; second, roundup doesn't receive the replies, so they are not appended to
the issue.

I think one simple possible fix is to stop setting reply-to on darcs-devel.
Replies to issue mails on the list would then (I believe) go back to roundup, be
appended to the issue and forwarded to darcs-devel as usual. (At least, once
http://bugs.darcs.net/issue1085 is resolved.) 

I don't think we need darcs-devel to set reply-to darcs-user - self-discipline
is sufficient, in practice nobody replies to buildbot mails, and the reply-to
doesn't prevent occasional misdirected mails anyhow.

Jason, any reason not to give this a try ? Otherwise what to do about this bug ?

I have changed the default reply-to to be poster, as per Simon's request.

Closing this bug for now.