Comment by radlad

Isn't the problem that this allows for all kinds of forms of insider trading?

> Insider trading—the practice of buying or selling a company's securities based on material, nonpublic information—has long been a contentious issue in financial markets.

https://www.investopedia.com/terms/i/insidertrading.asp

There's also a question of whether they are good for the health of the overall market: https://www.cbsnews.com/news/finances-dark-pools-explained/