The note_filter parameter allows one to have a different body section for a nosy message. It could be modified to allow one to change message properties. That would only be used for the UW trackers. This is a small snippet of ansible code that comments Precedence bulk the line out:

  - name: comment out prececence bulk
    lineinfile:
      path: "{{ TRACKER_SRC }}/roundup/mailer.py"
      regexp: '^(\s*.*Precedence.*bulk.)$'
      backrefs: yes
      line: '#\1'

It gets applied after the roundup code is untarred on the tracker host. This way I can keep up with the roundup tip and still be able to have nosy emails not dropped by the UW changes to mailman.