Would be interested to see real numbers around societal value from marginal added liquidity versus aggregate spend into the zero sum arms race.

I have also seen enough to be quite sure that many hft strategies are quite normie investor predatory.

Again, I’m not zealot. I trade stuff. I love liquidity. I’m happy to pay someone some fraction of a penny to change my mind. Service provided. But the returns from vanilla liquidity provision commoditized long ago to uninteresting margins. That leaves a lot more of the hft alpha pool in the predatory strategies and capital flows where the incentives are.