The only way to 'manipulate' the price, is by either buying or selling. They'd be bonkers to buy, the consequence of that is just giving away money, and judging by the price, clearly they are not selling in any meaningful quantity.
my conclusion, too.
i am asking, because sometimes there are not so obvious 'backdoors'.
Maybe, they've done it before, but why would they? It just costs them money for no obvious benefit.
if the GHS-shares dont generate profit midterm (maybe for one, two months) and they dont adapt and improve efficiency, the shares will loose their market value. this will happen soon, if btc-price stays at ~300$ and difficulty increases around 10%, 15%. see calculator at bitcoinwisdom.
in this case they can buy the shares back for nearly nothing and mine for themselves. and on the longer run they will 'run' into the profitability problem by themselves.
i personally think, they have some room to lower the fees and reduce their own profits for some time. i also think, that in the very near future the btc/usd-price will start to react to all the moderate positive news of the last year.