Billionaire private equity mogul David Bonderman crashed a rival’s party on Tuesday — stopping an alleged sweetheart deal in the $80 billion middle-market lending sector. In an upset, Bonderman’s TPG Global convinced shareholders of one embattled lender to reject the sale of its management arm to Jonathan Nelson’s Providence Equity Partners — even though leading shareholder proxy service ISS recommended they OK the deal. The management arm, TICC Management, is a highly profitable piece of the lender, pocketing hedge fund-like fees of 2 percent of assets and 20 percent of profits. With $1 billion in loans, that comes to about...