On (2), I think I say a bit about this in the piece, but my guess is that it’s not much easier to launch debris from the Moon into Earth orbit, than to launch it from Earth into Earth orbit. Although the Moon has the “high ground” in some sense, you need to decelerate the debris to settle into low orbit, which requires some kind of active thrust near periapsis. My sense is that launching debris from Earth to orbit around the Moon is even harder — both because Earth is stuck in a bigger gravity well, and because the Moon is gravitationally lumpy.
(3) is an interesting point. But, as I say, I don’t think a debris cascade is very likely to actually trap civilisation on Earth for any meaningful amount of time. Somewhat more likely is if a first-mover used it to make catching up more expensive, after they themselves escape Earth. And more likely still is that it’s (as you say) conflict promoting for more prosaic natsec reasons, or the result of a conflict and ∴ evidence civilisation is in a bad state. Either way, it seems good to prevent on trajectory-improving grounds too, in my view.
On (2), I think I say a bit about this in the piece, but my guess is that it’s not much easier to launch debris from the Moon into Earth orbit, than to launch it from Earth into Earth orbit. Although the Moon has the “high ground” in some sense, you need to decelerate the debris to settle into low orbit, which requires some kind of active thrust near periapsis. My sense is that launching debris from Earth to orbit around the Moon is even harder — both because Earth is stuck in a bigger gravity well, and because the Moon is gravitationally lumpy.
(3) is an interesting point. But, as I say, I don’t think a debris cascade is very likely to actually trap civilisation on Earth for any meaningful amount of time. Somewhat more likely is if a first-mover used it to make catching up more expensive, after they themselves escape Earth. And more likely still is that it’s (as you say) conflict promoting for more prosaic natsec reasons, or the result of a conflict and ∴ evidence civilisation is in a bad state. Either way, it seems good to prevent on trajectory-improving grounds too, in my view.