The above paragraph is pure drivel.
First, and most obviously, hedge funds buy shorts to hedge their bets on longs. They short one thing, to hedge against losses on the other things they're long in. They don't short the same investments they're long in. That would make no sense — you'd do better by making no trades at all.
Second; the writing is totally biased, in a smarmy, propagandist style. “Questionable but legal practice” — questionable by whom? Ignorant communists?
If some large speculator (say Soros), takes out a huge short position; and then proceeds to destroy (say) a country's currency — that would be illegal (for ordinary folk). Such a practice would be equivalent to pumping a stock you're long in, in the hopes of dumping it at a higher price. Going short, without subsequent attempts at market manipulation; is no more “questionable” than going long, without attempting to manipulate the market.
It's disingenuous, at best, to conflate legal short-selling with illegal market manipulation.
I'm not qualified to discuss the more technical aspects of trading, so I'll leave that conversation to others. I posted the article so that financially educated people like yourself could shed some light on this.