Pat, I agree that status may make a difference however if Qantas does segregate and not treat a passenger, with a reasonably simple request to the best of their ability, what chance do they think they have of that passenger ever becoming a Platinum member.
The circumstances whereby a passenger has multi segments then requests to forgo an initial segment and join the itinerary at one of the other segments, should not be an issue, provided the airline is given sufficient notice. Airlines who do not support this issue are merely being difficult.
I often think that Qantas forgets that they do not rule the Australian sky.
I guess it is just worth making sure the simple request actually was one. I would still maintain that dgwally should have gone through the travel agent as they 'own' the booking. TAs rely on this ownership for their business and their relationship with their clients. A good agent should able to resolve these situations with the airline more easily than the passenger. That's the reason you'd use one. Otherwise, you'd be better to book directly.
The issue of the agents being unresponsive or uninterested is a separate one and the behaviour described could not be condoned. I don't know that status actually does make a difference, but the premium service has definitely improved in my opinion.