I agree with the principle of share buy back and what it does, however, in this case, there was a company loss, not a profit. Cash reserves, in Qantas's case were meant for new aircraft, infrastructure improvement and the like, but not a buy back.
Buy backs are good policy when a company has billions in profits not returned to shareholders by dividends e.g. CSL and Rio Tinto, and no viable opportunities for adding businesses to their portfolio.
As to the shareholders, they would have been better served with a fully franked dividend paid from the reserves that this ill considered buy back is financing.
The plan to retire some debt early has merit, but I would think the need to retire some aircraft early would be better.
Bending the rules or not, a buy back is still dumb.