(Bloomberg) -- Som Seif, the entrepreneur bent on disrupting Canada’s financial industry, has found himself at the center of an unprecedented showdown with the country’s top markets watchdog. The asset management executive is a consummate marketer — a skill that helped him build a firm that was one of Canada’s early winners in exchange-traded funds, sell it to BlackRock Inc., then start another, Purpose Investments Inc.  But that knack for self-promotion has caught the attention of the Ontario Securities ...