In 1997 I used to trade through TD bank and for shorting, I had to call them. When I called the local branch, they did not ask my account number as they already had it by heart. I had also personally met them. One of them told me that he shadowed one of my short trades but since as an employee he could not hold the position longer than a certain period, he closed the position at a loss.
Conclusion: They can do it but as other respondents mentioned, you cannot 100% be sure that the trade will be profitable. Some traders also trade from multiple accounts so they cannot be chased . Short in one account and be hedged in another account through another broker.
Conclusion: They can do it but as other respondents mentioned, you cannot 100% be sure that the trade will be profitable. Some traders also trade from multiple accounts so they cannot be chased . Short in one account and be hedged in another account through another broker.

