Talking of the Army Rumour Service, on the subject of popularity of the SIB, the ARRSEPedia entry at http://www.arrse.co.uk/wiki/SIB
"People to generally be avoided as they make the SS look like the Women's Auxilliary Balloon Corps."
They are presented more sympathetically in the TV series about the SIB in Germany called "Red Cap".
If you get "BBC Entertainment" (e.g. on on Kabel Deutschland), it may be repeated some time.
I don't know if there's anything special about
- "If ever the SIB talk to you, you should say 'No comment, I want a lawyer.' Alternatively, a simple 'Thank you for noticing me' will suffice."
except jocular advice about what to say when addressed by the SIB: "Kein Kommentar. Ich will meinen Anwalt sprechen."
I would guess the alternative also means "know nothing, say nothing", but in an exaggeratedly deferential way, on the lines of "Danke, dass Sie meine Wenigkeit bemerkt haben!"