The real estate middleman confirmed what many would expect to be the case. It even doubled down on the resulting opportunity.Largely in response to news regarding its ever-strengthening place within the real estate sales business, data from S&P Global Market Intelligence indicates that as of 3:54 p.m. ET Monday, Redfin (RDFN 12.03%) stock was up 11.4%.More upside could be in store, too.It's complicatedLast month, the National Association of Realtors (NAR) changed long-standing rules regarding agents' commis ...