Hi Redpanda,
I agree - one should never fly through significant volcanic ash.
I do not believe that we have significant volcanic ash over Australia at present.
The airline operating manuals also state that flight should not be conducted through thunderstorms and micro-burst and so forth. Which is not interpreted by the general aviation community as as reason to cancel all flights. We are (I thought...) smarter than that. We understand that the danger in these phenomenon is specific and identifiable and definable.
Where is this supposed 'boogey-man' of a volcanic ash cloud? It would be different if it was in Indonesia or New Zealand. But, for goodness sake - this ash cloud (for want of a better word) has come from South America. And, it hasn't even come the shortest route - it's come via South Africa.
It is so dispersed it is unidentifiable.