The Reddit hordes were at it again Friday, once again bidding up shares of GameStop Corp. and warring with hedge funds by seeking out targets such as Siebert Financial Corp. and Twinkie maker Hostess Brands Inc.

Hours after Robinhood Markets said it received a cash infusion of more than $1 billion, having just angered legions of retail investors by imposing a raft of trading restrictions, the Securities and Exchange Commission said it would look to identify potential misconduct and review decisions by brokerages to curtail transactions on certain stocks.