Activist investors brave enough to have ventured into the volatile energy sector are paying a heavy price for their courage, stuck with hefty paper losses and no near-term recovery in sight. Corvex Management, Elliott Associates and ValueAct Capital are among the largest and most prominent activist firms that have seen the value of their energy holdings tumble in step with sliding crude prices and remain exposed to the price rout. Activists, a growing class of mostly hedge fund managers who buy up minority stakes in companies and push for major changes, historically steered clear of stocks exposed to the volatile commodity sector. Such funds often operate with a shorter time horizon than most investors, making them more vulnerable to sharp price swings. But beginning around five years ago, some activists saw opportunities in the energy sector that seemed to outweigh risks when oil traded at around $100 per barrel. […]