Truly and thoroughly upside-down.

Actually, also as an Australian:

I'm pretty sure this is one of those things that's true in the Northern half* of the country that people think applies everywhere, like crocodiles and jellyfish that kill you. I've lived in SA and Vic all my life and all my friends would just be insulted if I called them cunt instead of mate.

* "Northern Half" of course meaning above the Barassi Line and probably adding the NT, not the real geographic north.

Depends on the circles of friends really. But yeah that one definitely isn't a country-wide rule if you plan to keep all your teeth