Time limits do make sense, but this destroys the high frequency trading market. HFT makes money for the market and provide liquidity. It is valid that they have speed limits, the market just needs to be prepared for them to disappear overnight.

Cancelling before execution is a bad design? Maybe a rate-limiter can exist to detect too many cancelled orders at size, but I cancel orders all the time because I see a better trade or realize it won't fill any time soon. I should have to keep the orders up all day, according to thos rule you propose?

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