To a first approximation, no non-affiliate investors ever get in trouble for publicly saying nice things about stocks they are long. Short sellers, on the other hand, do. This is a problem even if you’re right, but it’s a big problem if you’re wrong, as sometimes people are. Shorting a company and publicly calling it a fraud, if it turns out not to be a fraud, is the sort of thing that gets you sent to jail for market manipulation.
But what if you just ask innocuous questions on a conference call? No one could possibly read Einhorn’s questions to Herbalife as any sort of factual assertion that Herbalife is in fact Bad. Here is the silly minimal version of the trade: company announces earnings, stock doesn’t move much. There’s a call at 11am. You short the stock. You get on the call. You ask questions like “why are you no longer disclosing what you used to disclose?” The company answers “because it’s not helpful.” You’re all “thanks.” You hang up. The stock drops 20%.