I worked at a market maker (owned by a bank) that handled around 8-10% of US stock trades. When things like the flash crash happened, the strategy was to stop anything automated, because the simple strategies had no way of knowing the cause. Trading on normal market-microstructure signals, the trading that provides the bulk of liquidity, would just get you creamed.

To meet our market maker requirements, which allowed us to do things normal market participants can't do, like naked shorting, we would do things like leave a 1 penny bid and ten-thousand dollar ask and not change them for the entire day. Exchange regulators tried to address this and made market makers quote within some percentage of the bid/ask. Nasdaq literally just created an order type that would automatically reprice itself to always be exactly that percentage away from the bid/ask, so that it could never execute--just like the previous 1-penny bids--but would comply with the regulation. The order type only existed to bypass that regulation and was literally created in response to demand after its passage.

Even without that order type we'd just do (and did do, it took them a while after the regulation to add the order type) the same thing in the models' trading logic.