> 1. non HFT traders are the fundamental players in the market, without them, HFT traders wouldn't exist. The exchange itself wouldn't exist. The exchange's obj

> 1. non HFT traders are the fundamental players in the market, without them, HFT traders wouldn't exist. The exchange itself wouldn't exist. The exchange's objective is to connect non HFT traders. Sure: there are buyers, sellers and market makers. Naturally the market exists for buyers and sellers. Market makers can't exist without anyone to make a market for, and buyers and sellers can't exist without a way to find each other (more generally, the market requires liquidity to be healthy). The market is an ecosystem. Market makers used to make markets in timescales that required me to wait minutes before I could complete an order. Now I can wait less than a second. So this brings us full circle back to my question: if they benefit the market at sub-second granularity, and you can't demonstrate a harm in sub-millisecond granularity, why do I want them to stop? > 2. subsecond liquidity is useful because non-HFT traders want their orders to be done as fast as possible: they want to their orders to feel immediate. Yep, I'm with you there. > 3. non HFT traders do not care about submillisecond liquidity because the timeframes in which they invest is much larger. And now you've lost me again; I am an active algotrader, and I don't work in HFT timescales, but I appreciate the liquidity benefits I get from HFT all the same because I do trade in timescales that make it meaningful. Furthermore, I can't really consciously think productively in sub-second or sub-millisecond resolution. Retail investors who trade by hand don't need sub-second or sub-millisecond resolution. If you have an argument that both are harmful, make that argument. If you have an argument that sub-millisecond is harmful, make that argument. But so far you're saying it's bad because...people don't need it, which is odd. I don't really try to stop people from doing things that I either don't care or about or which don't harm me. There's a lot of that in the world. > 4. submillisecond liquidity is harmful because it incentivize HFT firms to stupidly race to reach the exchange without adding any value for the non HFT traders, while at some point the exchange has to say "we received these 2 orders at the same time". I'm still not following you, because you're not demonstrating harm here. It's harmful because it's stupid? Why is it stupid? Who can deem it to be stupid? Even if it is stupid, what makes it actually harmful to anyone? As to your last point, what do you think is more likely - timestamp collisions at second, sub-second or sub-millisecond resolution? Frankly your point here is an argument for greater resolution, no lesser.