TBH, I still don't get it. Perhaps if I saw L2 day in and day out and compared it to other stocks I'd understand what you're talking about. But if they sell short then cover quickly, the net effect should be zero. -1 + 1 = 0, right? So how does the stock that is just waiting to unleash to the upside by natural forces of supply and demand be pegged by HFT selling short and covering immediately?