The responsibility to comply with the Official Secrets Act lies with the individual.
You'd (in the main) make mincemeat of anyone trying to pin an official secrets rap on you based upon the contents of pprune posts, methinks.
Pprune ain't exactly the Clive Ponting Affair, is it.
I dare one of you (serving bods) to open a Number 10 Petition, "That DIN xyz be withdrawn in the interests of free speech and good banter".
CG
"The practice of referring to Falkland Islanders as 'Bennies' is to cease forthwith". That worked too. Didn't it?