It is quite risky to trade ETC. You do not know when the DAO hacker will dump his ETC and if he is part of the ETC whales.
Source? Seems like this would be shooting himself in the foot, and the guy is obviously a competent trader, that short was a work of art. Why would he supress the price of an asset he is a major holder of, when there is an obvious uptrend in progress? And what books would he even dump on? Polo? I think they would see the incoming deposit and figure out who it is.
It is possible the hacker is involved in the ETC initiation. Otherwise, no other people dare to pump the ETC.
If he did then now we know part of his motivation is to bring The Ethereum fork down. I speculated that his motivation is to destroy Vitalik's Ethereum because the hacker might be a bitcoiner. There is also news that the attacker is Mircea Popescu. He is an oldschool bitcoiner and he is feared by everyone even Vitalik himself.