It seems that some of the QF terminal agents are still enabled to both think and act at their discretion, contrary to some of the comments you hear. I had made a mistake with my son's trip. He's a bronze FF and "always before" we had checked his sporting equipment as oversized baggage as a second piece of luggage (travelling across QF, JQ, VA and now also Rex).
In Sydney T3 this evening, we went to print luggage tags from a kiosk. It printed out one and then wanted $100 for the second one - because he was entitled only to a single checked baggage for free. We dropped off the "main" luggage (whopping 6 kg) and then went to the oversize desk to the second bag. The agent there took it in and directed us back to the kiosks to pay the fee. I couldn't get the kiosk to co-operate, waved an agent over and she got me started. However, the process stalled and I needed her help again. She took us over to her station, tapped on the computer and realised the silliness of charging extra for a 2 kg bag on top of a 6 kg bag. More tapping away and my son got his second bag through for free.
Looking at the baggage rules, a single bag of 23 kg, yes. My mistake of overlooking it and was ready to pay for it. But it was nice to see that an agent on the floor can also use their own judgement and has the permission to change things, when it's sensible. Many thanks for that middle-aged lady with Italian background.