Market participants may have misinterpreted comments by U.S. Securities and Exchange Commission Chair Gary Gensler about payment for order flow. Gensler told Barron’s that a ban on that practice is “on the table” because it generates “an inherent conflict of interest.” Shares of Robinhood Markets Inc., Charles Schwab Corp. and other brokerages most dependent on payment for order flow promptly dropped. But Gensler’s next sentences changed his meaning significantly, and Robinhood may not be the firm most at risk.

Williams Spoke to John Lothian News for the Open Outcry Traders History Project Bruce Williams met Blair Hull when both were on a joint CBOT-CBOE committee for a new equity product where different versions would trade at the exchanges. Williams was in the Major Market...