Languages, it is said, are never static – words, their meaning, their pronunciation and preferred syntax are constantly evolving. But the changes are not restricted to words – punctuation marks too, evolve. Take, for a recent example, an unusual construct from an official US Govt. source – reprinted by the UK Guardian as part of their ongoing mass-communications surveillance revelations. [Aug. 09, 2013]
“… analysts may NOT/NOT implement any USP queries until an effective oversight process has been established …”
Note the unusual use of the forward slash – a.k.a. [the] Stroke, Oblique, Frontslash, Separatrix, Slak, Slant, Virgula Suspensiva etc etc.
Improbable has consulted two highly respected authoritative sources in an attempt to interpret it, viz. Punctuation Matters: Advice on Punctuation for Scientific and Technical Writing, by John Kirkman, and Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation, by Lynne Truss. But, sadly, neither provides any firm lead. Nevertheless, we offer the following observations.
 The most usual meaning of the slash is as an abbreviation for ‘exclusive or’ , e.g. “ham/cheese” – but in this case it can’t apply because the two alternatives either side are identical.
 If the slash was absent the sentence would make perfect sense – As in “Please do NOT NOT use the footpath” which would mean “Keep off the grass”
 What if the slash wasn’t a slash – but instead a Solidus, conveying the meaning ‘divided by’ ? Unfortunately, the sentence still doesn’t parse. NOT [divided by] NOT would surely be 1 (or, at a stretch, infinity).
NOTE: If you do manage to decrypt the sentence please do NOT NOT NOT send your results to Improbable (except by carrier pigeon). We have reason to believe that this website is being monitored by members of the public.
ALSO SEE: (possibly partially pertinent) On the presumed competence of British (and other) spies (Improbable Research, August 11th, 2013)