That the horizon will invariably form (and by "form" I mean "have enough matter fall into it to consist of a black hole even if all the matter still-outside of it suddenly disappeared") at a size much larger than quantum gravitational effects could matter.What point? That whatever quantum gravity effects become important at the singularity won't affect the formation of the horizon?That's the point I'm questioning.
Ah, I see. I think I'm getting a better picture of things.No. You are still thinking about things from a static viewpoint--that's the viewpoint that says ingoing radiation gets blueshifted and outgoing radiation gets redshifted. But a collapsing configuration is not static, and your intuitions about a static viewpoint don't work.
Just as one example: a static observer very close to a static black hole's horizon sees incoming radiation highly blueshifted; but an infalling observer falling past that static observer sees incoming radiation redshifted, not blueshifted. This is still a static situation overall, so it doesn't fully capture what is going on in a collapsing star; but at least it illustrates that static intuitions can't be applied to infalling objects.
Would it perhaps be accurate to say something like "the solutions to the Oppenheimer-Snyder model of collapse prevent a discontinuous event horizon; all the components of a gravitationally collapsing object will perceive the event horizon swallowing them up simultaneously"? Or something along those lines?
Of course, I'm not interested in the event horizon for its own sake; I'm really wanting to know at what point the conditions for the creation of Hawking radiation are met. Because Hawking radiation can't be teleological. I guess this is a restatement of the firewall problem....