Note that Holden qualified his statement with "(too often)".

And the point which I was making was that EEV does not do this too often, it does it just often enough, which I think is pretty clear mathematically.

Then investigating the cost-effectiveness of intervention A comes at an ostensible opportunity cost of X/10. But it's ostensibly the case that the remaining $900,000 could in no case be spent with cost-effectiveness within an order of magnitude then spending the money on intervention A. So in the setting that I've just described, the opportunity cost of investigating is ostensibly too high to justify an investigation.

I don't see what you're driving at with the opportunity cost of X/10. Either we have less than $1,100,000 in which case the opportunity cost is X or we have more than $1,100,000 in which case it is zero. Either we can do X or we can't, we can't do part of it or more of it.

The fact that naive EEV leads to this conclusion is evidence against the value of naive EEV. Of course, one can attempt to use a more sophisticated version of EEV; see the second and third paragraphs of Carl Shulman's comment here.

If naive EEV causes problems then the problem is with naivete, not with EEV. Any decision procedure can lead to stupid actions if fed with stupid information.

See my fourth point in the section titled "In favor of a local approach to philanthropy" here.

You make the case that local philanthropy is better than global philanthropy on an individual basis, and if you are correct (which I don't think you are) then EEV would choose to engage in local philanthropy.

It's not humanly possible to take all factors into account; our brains aren't designed to do so.

The correct response to our fallibility is not to go do random other things. Just because my best guess might be wrong doesn't mean I should trade it for my second best guess, which is by definition even more likely to be wrong.

implicit knowledge which is inexplicable

A cognitive bias by another name is still a cognitive bias.

My intuition is that in the real world the incentive effects of using EEV would in fact be bad despite the point that you raise; but refining and articulating my intuition here would take some time and in any case is oblique to the primary matters under consideration.

I agree that it isn't very important. Regardless of anything else, the possibility of more than a tiny proportion of donors actually applying EEV is not even remotely on the table.