Both the "require DKIM" and the mailing lists problem were discussed at length by the working group, with many having opposite strong opinions, so in the end the only consensus that was reached is a trade-off that left everyone unsatisfied.

There's hope that the mailing list problem will be solved by DKIM2 [1], since ARC has the problem of trusting the intermediaries.

On `pct`, you're right in theory, but it seems that implementers didn't get the message. From the mailing list [2]:

> That's how we intended it when we wrote that, and that's how early implementations did it. But maybe this is the lesson: People have inferred lots of different things from that rather straightforward definition, so maybe it's more ambiguous than we realized all those years ago.

And the draft says [3]:

> Operational experience showed that the pct tag was usually not accurately applied, unless the value specified was either 0 or 100 (the default), and the inaccuracies with other values varied widely from one implementation to another.

I agree that replacing it with another tag is such a confusing and unnecessary change, though.

[1] https://datatracker.ietf.org/doc/draft-gondwana-dkim2-motiva...

[2] https://mailarchive.ietf.org/arch/msg/dmarc/Sk6JnDlXH_MkM4xm...

[3] https://datatracker.ietf.org/doc/html/draft-ietf-dmarc-dmarc...