The context of the comment being a Jane Street blog post is why I singled out HFT.

I think we're probably roughly in alignment w.r.t. other forms of finance, but the market liquidity gained by a marginal HFT employee almost certainly isn't worth the marginal cost imo. Even in finance, you could do a lot better by expending that human capital into optimising the structure of the markets themselves (there's lots of research on how hideously inefficient the TSE is because of its coarse tick sizes, for example; but vested interests get in the way of fixing that).