I wouldn't consider eating any of it past medium, past that it's just burnt meat and burnt meat doesn't taste good. Medium is questionable for edible in my book. Risk and reward, I feel safer eating wild game rare than anything you can buy. We all take risks, it's a risk to leave your house in the morning, it's also a risk to stay there. It doesn't matter what you do, there's a risk to do it. That said, that stuff freaks me out a little bit.....not enough to ruin a good steak though. I'll eat tofu before I eat an over cooked good steak....and I'll never eat tofu. There is plenty to worry about these days, eating good meat cooked right isn't one of them for me.will have to check, but I thought certain temperatures denatured the prion to the point it was not a threat. Not like I would ever consider eating meat that had CWD.
If it can be cooked out, it'll be ashes. Prions don't die, they are just a protein, I suppose once you get them hot enough that they are no longer a protein maybe you can eat them, but at this point, your meat is not meat anymore.