Three otherwise innocuous words -- reverse stock split -- can cause much disappointment and even sow panic in an investor community. Shareholders of clinical-stage biotech Agenus (AGEN -29.54%) experienced this vividly on Thursday when their company announced its intention to start going down that road. The stock's price fell sharply, by almost 30%, contrasting with the 0.6% gain of the benchmark S&P 500 index. Twenty shares will become one In a regulatory filing and a letter to its shareholders, both publi ...