[tex-eplain] Problem with marks and \doublecolumns

[Karl Berry]

    Since multiple columns use \output, I would say that
    implementing this feature would probably require a solution that doesn't
    use \mark.

I had the vague idea that maybe the double-column output routines could
take special care to preserve the marks when it "internally" calls the
fake \output. I'm not sure it's possible ... anyway, maybe someday, but
probably not, at least by me :(. --best, karl.