I think that if your argument is "because Harry screws up spectacularly, spectacular screwups are part of high rationality," you may not be reading MoR correctly.

Er, not quite. I'm saing that learning from spectacular screwups is part of rationality (in the same way that getting your arm twisted in two isn't part of the discipline of weight lifting), and that aspiring rationalsits are bound to make those in the process of learning to properly calibrate for risks. To use another metaphor, falling part of learning to walk, but not part of walking.

However, if you're doing prakour, which is like super-duper-awesome-optimized-walking, you're bound to get an Epic Fail every now and then. You shouldn't, but, as a matter of fact, you do, and it's funny because you've attempted something amazing and failed amazingly. If you hadn't attempted something amazing, your failure would have been much smaller, and much less interesting and amusing.

If you control for power, then one would hope intelligence would decrease the hugeness of mistakes (in distribution, at least).

Well, yes, the relative amount of mistakes VS successes would be smaller, but the absolute load of mistakes would be greater. There's only one way to never make mistakes, and it's to never leave one's comfort zone, which I feel is not how one should lead one's life, if one wants to grow.

I disagree with your political example, but do not see a reason to argue it here.

Fair enough. That it's arguable doesn't mean we have to actually argue about it.