Even when issued through an Australian agent, an airline is involved in the issue process. Normally an Australian TA is going to use QF for that process. And yes, I have plenty of stories of needing to advise the TA of the rules when the airline has not understood them properly.

But occasionally the airline and TA can make a mistake and issue a ticket that is not completely in compliance with the rules. When that happens, you just keep quiet, ensure you don't need to have the ticket re-issued (until after the mistake segment) and enjoy the benefits of the mistake (maybe some more on that topic when I complete this DONE4).

As for the need to include AA for MEL-LAX, that is due to revenue allocation. The various airlines are allocated a percentage of the overall fare based on the proportion of miles flown on each airline. So by changing to the AA codesahre, AA gets a bigger proportion of the renevue from the fare. Probably a good penalty against QF for not doing the right thing with the ticket issue in teh first place.