Is this rationality, or the politics of two-year-olds with nukes?

Is this a constructive point, or just more gesturing?

It is a gesture concluding a constructive point.

You're very focused on Wei Dai's statement about backward induction, but I think you're missing a key point: His strategy does not depend on D reasoning the way he expects them to, it's just heavily optimized for this outcome. I believe he's right to say that backward induction should convince D to comply, in the sense that it is in their own best interest to do so.

This is a distinction without a difference. If H bombs D, H has lost (and D has lost more).

If both countries precommit, D gets bombed until it halts or otherwise cannot continue development.

That depends on who precommits "first". That's a problematic concept for rational actors who have plenty of time to model each others' possible strategies in advance of taking action. If H, without even being informed of it by D, considers this possible precommitment strategy of D, is it still rational for H to persist and threaten D anyway? Or perhaps H can precommit to ignoring such a precommitment by D? Or should D already have anticipated H's original threat and backed down in advance of the threat ever having been made? I am reminded of the Forbidden Topic. Counterfactual blackmail isn't just for superintelligences. As I asked before, does the decision theory exist yet to handle self-modifying agents modelling themselves and others, demonstrating how real actions can arise from this seething mass of virtual possibilities?

Then also, in what you dismiss as "messy real-world noise", there may be a lot of other things D might do, such as fomenting insurrection in H, or sharing their research with every other country besides H (and blaming foreign spies), or assassinating H's leader, or doing any and all of these while overtly appearing to back down.

The moment H makes that threat, the whole world is H's enemy. H has declared a war that it hopes to win by the mere possession of overwhelming force.

Speaking of nuclear proliferation and its consequences, you've been pretty silent on this topic considering that preventing proliferation is the entire motivation for Wei Dai's strategy. Talking about "murdering millions" without at least framing it alongside the horror of proliferation is not productive.

I look around at the world since WWII and fail to see this horror. I look at Wei Dai's strategy and see the horror. loqi remarked about Everett branches, but imagining the measure of the wave function where the Cold War ended with nuclear conflagration fails to convince me of anything.