In your letter dated Sat, 24 Dec 2016 13:45:12 -0500 you wrote:
As I mentioned before, for me, the most usable option is avoiding
message modification of any kind, which leaves the origin DKIM
signature valid. I've not seen anyone comment on whether that's
workable for IETF WG lists (it works well enough for *this* list).
For me, the current behavior of the ietf lists is perfectly fine.
It is very nice to see the mailing list in the subject. It is also
very nice to have a proper From header.
That's why I proposed a per-subscriber setting such that only those
who are actually stupid enough to reject or otherwise drop mail based
on DMARC have to see mangled mailing list traffic.
There no technical reason for a one-size-fits-all solution. So let's
stop investigating those types of solutions.