Jane Street is not a huge player in HFT, they are primarily a liquidity provider and therefore actually do enable people to sell stocks during a crash. Any regi

Jane Street is not a huge player in HFT, they are primarily a liquidity provider and therefore actually do enable people to sell stocks during a crash. Any registered market maker has specific rules imposed by the exchange about always needing to provide a 2 sided offer within a reasonable bound of the current market.