Hello, it's been a while but I've had some positive progress in this issue.
Qantas latest email response to me said that they still claim I purchased a non-refundable fare however they will make a one-time exception for me and have processed a refund for the remainder of the fare (the tax component was already refunded). Whilst they're still wrong, at least they say they're sending my money back. I have a small concern as the email quoted an amount in AUD but I had paid in CAD. I'm just hoping that's a typo and I will see the correct amount come back to my credit card soon.
The process to get here after the bank advised they couldn't reverse the transaction was to go to my local consumer regulator (CBOS Tasmania) who were actually quite helpful. Someone at CBOS took up the issue with Qantas which resulted in Qantas eventually making an offer to provide a voucher for the remainder of the fare.
Trying to make the long story short - I turned down the voucher offer. There was a little more backwards and forwards where one of their responses was word for word the same as a much earlier email in the whole issue, which made it seem like I wasn't even writing to humans. Around this time I got some advice from a relative who is a solicitor who made a very good point that I had not yet got any confirmation that my complaint had been passed to the Qantas legal team. So my last email simply asked for the complaint to be passed to the legal team, and I named their head of legal as well, and I requested them to confirm to me when that had been done. Their next response was to advise they had processed the refund.