That’s not true. High frequency trading is the reason why the spread between buying and selling is so low. They compete to get your order. But you do loose money to these traders each trade you do. Even if that’s actually play in your favor.
It’s not what I am saying. I am saying high frequency trading will take most orders (including yours, mine, automated or not) from all exchanges no matter what, so you lose money on every trade. So having a bot that trades a lot will just make lose money for sure.
I was saying it isn't an applicable caution if you don't know what the person is trying to do with automated order creation and management. If they just want to set limit orders to their dynamic screener and ride them for two quarters, successfully, then the worse fills from the presence of HFT is no different than the worse fills that a human would get because everyone gets worse fills from HFTs if you don't route orders to the closest exchange exclusively.
Therefore saving that comment for a thread about trading algorithm isn't really any more relevant than saying it in any thread about trading.
