Highly paid hedge fund managers have complained for years that it’s unfair to compare their performance with the broad stock market during prolonged bullish periods. Hedge funds are designed to mitigate risk, the argument goes, and so investors in them might sacrifice some gains as markets rise while waiting for hedge funds to prove themselves in more challenging times. So far this year, stock markets have delivered weak returns, bond markets have turned in negative performances, and everything is much more volatile — just the environment that many hedge funds say they’ve been waiting for.