jira.codehaus.org can now accept comments to issues through email. When replying to a mail notification from Jira, if you include jira@codehaus.org on the recipient list, jira will add your email as a comment on the issue. It simply finds the issue key from the subject: header.

Now, all of those conversations started on lists as a the result of a mail from Jira will be saved for posterity's sake.