Boaz Weinstein, the hedge fund manager famous for betting against the JPMorgan Chase trader known as the “London Whale,” is being accused of his own accounting chicanery. In a case that could have chilling lessons for investors in certain kinds of illiquid assets, Mr. Weinstein — a chess master who made his career exposing and gambling on mispriced assets — is being sued by the Public Sector Pension Investment Board of Canada, formerly the largest investor in his hedge fund, Saba Capital. The pension fund sought to liquidate its investment in Mr. Weinstein’s fund earlier this year after he piled...