Esoteric languages is often a good screener for good devs.

A large talent pool isn't necessarily a positive if you don't spend a lot of effort on your recruiting (mostly filtering) process. It really just increases the risk of bad hires.

That makes sense to me. But, in light of that, the ones who do go to Jane Street are relatively more likely to be interested in their tech stack and OCaml, as opposed to wanting to "test themselves" in the "adversarial setting" that the post I quoted describes. In contrast, the couple of people I know who went to HRT or Jump Street are much more like that description. They deliberately targeted HFT work, whereas Jane Street has more people who "fell into it" because of this outside interest.

I mean, Yaron used to go around a lot and give guest lectures about OCaml programming "in industry" at all sorts of functional programming courses in universities. I have to imagine they thereby recruited people who would have never considered HFT shops otherwise.

A larger talent pool isn't always better.

Every few months or so I run out of patience with C++ and wonder about the alternatives, of which there seem to be very few in HFT. Jane Street stands out for that reason. It's a smaller talent pool but I don't think it's a subset of those that the C++ shops can attract.