[calderknight]

I don't think your interpretation of the sentence is sensible. The sentence mentions that the host knows what's behind the doors. So, if he is allowed to open the door with the car, the problem would become insoluble and would just be about speculating on the host's personality. And it definitely doesn't support the conclusion that the probabilities become 50/50.

[calderknight]

Not logical. It doesn't follow from the assumption that the host would not pose the question "Hey, here's the car, wanna switch?" that the contestant would automatically lose. You could just as well speculate that if the host opened the door to the car the contestant would automatically win the car.

[kragen]

it's pretty counterintuitive that his personality enters into it, isn't it?

[calderknight]

If the format of the game allows him to show the car to the player, how could his personality not enter into it? In every case where the player picks a goat-door, the host will be presented the option to either reveal the car or the goat. I mean, one can imagine various complicated scenarios in which the host might reveal the car exactly 50% of the time in such cases, but none seem like they can be reasonably arrived at.