At the airport, there is no procedure of getting compensation for domestic flights. It's basically either Y on the current flight or J on a later flight.
After the fact and only if the customer initiated the complaint, QF would highly likely just send one of their rubbish emails that doesn't even address the issue and say 'sorry'.
International is a different story and with $$ amounts for downgrades.
This is the really issue with your contribution. You're NOT stating what the situation is, you're just giving your opinion. That opinion is based on completely made up scenarios, where you think the "regrade" is justified. You've mentioned the pax getting their points back, is that based on you assuming they did a points upgrade? (I don't think you would have looked up the details on your insider system, because sharing such information in public... )And neither does the OP. The OP doesn't know anything about the downgraded passenger. They could've been a staff traveller for all we know. Unless it was the OP who was downgraded.
I'm not triggered at all, I'm just stating what the situation is.
However, here is the thing, how do you know they didn't buy a full fare J seat 1 hour before the flight? That is equally possible since no one knows the actual details, not even you. So you have have opinion and speculation.
Now in my opinion the fact that contradicts your speculation is the fact that the pax got on the plane with a boarding pass for seat 3A. Can you explain to us how that happens within the regrade system, hypothetically? Does qantas normal regrade people to 30A and still give them a boarding pass for 3A?
For mine that little detail would seem to indicate your opinion about what happened is no more reliable than any of the speculation in this thread.