I'll fix it for MM 2.1.15. I'll add digest_footer as the last RFC1153 message in the digest. I'm not completely sure how best to do this. I.e., should it be added as a message with an empty header, or with a single, non-standard (e.g.) "Footer:" header or with a "Subject: List footer" header. I lean towards the Subject: header, because it is clearly compliant with the RFC and probably works best in an exploded digest, but the empty header is probably best in an unexploded digest.