 SAN FRANCISCO--BUSINESS WIRE--Indaba Capital Management L.P. together with its affiliates, Indaba or we, which is the largest independent shareholder of MDC Partners Inc. NASDAQ: MDCA MDC or the Company, today issued the below open letter to Chairman and Chief Executive Officer Mark Penn regarding the Companys prospective merger with Stagwell Media LP Stagwell. In addition, Indaba has issued a presentation outlining why it opposes the merger on its current terms and plans t 