The shorts are playing a dangerous game. With Poet, we see the volume can drop off without warning. They think that is to their advantage as they feel they can put downwards pressue on the price due to low volume. But it goes both ways, since each downward push takes out the "weak hands" and reduces the sellers.

Once the herd is out, and the buyers start coming back in, the push upwards can be fast and quick, with no sellers left. This is one of the reasons why the stock is so volatile, bi-polar really, as the shorts move quickly to cover, competing with other "real" buyers trying to get in.