DKIM causing trouble with Tor lists, should be stripped
Tor Project list server does not remove DKIM headers and reliably modifies the Subject: header in such a manner as to produce DKIM validation failures. Beyond adding a prefix which can be anticipated by conscientious senders, spaces are injected at unpredictable offsets. This badly degrades spam-scoring of messages by Google and other ESPs and frequently results in the sending of list messages to spam folders.
My recommendation is that the list server configuration be set to completely strip DKIM headers from forwarded messages.
Possibly if the list server software supports it, a DKIM-signed RFC-7001 Authentication-Results: header might be added though it seems to me the positive effect on spam scoring would be minor, where in comparison not stripping DKIM headers results in a substantial negative impact.