Shares of casino operators extended recent sharp selloffs on Thursday, as J.P. Morgan analyst Joseph Greff added the insult of downgrades to the injury of tighter Macau regulations. The gaming companies with Macau-centric operations have been hit hard this week since the government of Macau SAR (Special Administrative Region), China, recently recommended allowing only gaming-license holders to distribute profits to shareholders, after receiving government approval, and for direct government supervision of gaming companies. On Thursday, J.P. Morgan’s Greff downgraded Las Vegas Sands Corp. LVS, -0.96% , Wynn Resorts Ltd. WYNN, -1.85% and Melco Resorts & Entertainment Ltd. MLCO, -0.73% ,...