Unsurprisingly, my post to the bug-groff email list (http://lists.gnu.org/archive/html/bug-groff/2018-10/msg00029.html) about how no one seems to monitor mail sent there anymore went unanswered.
Groff's documentation has been updated (http://savannah.gnu.org/bugs/index.php?54910) to direct bug reports to the bug tracker rather than that email list, but this change has not made it into a released version of groff yet, and even when it does, older groff versions will still point readers to a mailing list that no one reads. Is it possible to configure bug-groff to autorespond to any email that doesn't come from the Savannah bug tracker, telling the sender that the tracker is the preferred place to report groff bugs?