I don't understand what that Korsgaard quote is trying to say.

In the context of the larger paper, the most charitable way of interpreting her (IMO) is that whether we have free will or not, we have the subjective impression of it, this impression is simply not going anywhere, and so it makes no sense to try to figure out how a lack of free will ought to influence our behavior, because then we'll just sit around waiting for our lack of free will to pick us up out of our chair and make us water our houseplants and that's not going to happen.

I said that, when making a choice, you shouldn't consider, in your set of possible worlds, possible worlds in which you can't make that choice.

What if we're in a possible world where we can't choose not to consider those worlds? ;)

It's certainly not as confused a way of looking at things as choosing to believe that you can't choose what to believe.

"Choosing to believe that you can't choose what to believe" is not a way of looking at things; it's a possible state of affairs, in which one has a somewhat self-undermining and false belief. Now, believing that one can choose to believe that one cannot choose what to believe is a way of looking at things, and might even be true. There is some evidence that people can choose to believe self-undermining false things, so believing that one could choose to believe a particular self-undermining false thing which happens to have recursive bearing on the choice to believe it isn't so far out.