In 1950, Robert Hall published a popular anti-prescriptivist book entitled "Leave your language alone." (Everything isn't on the internet yet -- I couldn't find a review or even a summary on line!). By the mid-1960's, Hall's book was already a classic, which everyone in the field knew at least by name. So it was a plausible joke to make up a fake bibliography containing a sequence of polemics and rejoinders including the titles "Leave 'Leave Your Language Alone' Alone", "Leave 'Leave "Leave your Language Alone" Alone' Alone", and so on.
This joke satirized the passions of (anti-)prescriptivism, the polemical propensities of linguists, and the problems of center embedding.
What I can't remember is whose joke it was, or exactly how it was expressed. I believe that it was in a dittoed sheaf of similar in-jokes given to me by either George Lakoff or Haj Ross, and the author might have been Jim McCawley.
"The thing is," says Liberman, "I can't remember all the details -- but if I post what I remember, I hope that I can count on someone else to explain the rest." Of course he can.
The recursion in question appears in the book Studies out in Left Field: Defamatory Essays Presented to James D. McCawley on the Occacion of his 33rd or 34th Birthday, edited by Arnold Zwicky, Peter Salus, Bob Binnick, and Tony Vanek. One of the many linguistic in-jokes in this collection is something that purports to be the front cover of an issue of Language: The Journal of the Debating Society of America, "communicated by Carolyn Killean, George Lakoff, Robin Lakoff, Michael O'Malley, and Lester Rice." The third item in the table of contents is:
Paul Schachter: Leave "Leave LEAVE YOUR LANGUAGE ALONE Alone" Alone: A Reply to Pulgram's "Leave LEAVE YOUR LANGUAGE ALONE Alone"
SoiLF originally appeared in 1971 (it was reissued by Benjamins in 1992), which places it in the temporal gap between an influential article from the field of computer science and the famously recursively titled reply to that article. E.W. Dijkstra's "Go To Statement Considered Harmful" appeared in 1968, and Frank Rubin responded in 1987 with "'GOTO Considered Harmful' Considered Harmful" (see the Jargon File, s.v. Considered Harmful).
It might also be worth noting that Leave Your Language Alone is itself a derivative (though non-recursive) title, since it follows a pattern suggested by James Thurber's (1937) Let Your Mind Alone, in which the samblind humorist demolished various inane self-help and pop-psychology tracts of his day.