Andrew Daviel writes:
http://en.wikipedia.org/wiki/X-No-Archive says "If the X-No-Archive field is set to "No", or the field is absent, a Usenet archive will not recognize a prohibition on archiving the message."
Experimentally, if I add "X-No-Archive: no" in Alpine or Thunderbird, pipermail will not archive the message,
Do you consider that a bug?
I'm not sure why anybody would use "X-No-Archive: no" in reality, I wonder if it's a mistake in interpreting the double negation. But seeing it in Jeff's list, I guess people actually do use it. I wonder if Jeff would be willing to look at (some of) the 255 nos and see what fraction seem to have appropriate insemantics (ie, there is reason to believe the user was trying to prevent archiving, such as a "confidentiality" footer).