There is absolutely no shorting in OTC, none, zilch, nada, nothing whatsoever, the only one that short are Market makers and that is insignificant. Some institutions from offshore accounts short their own account if they have position in it to induce selling. For instance Sabby Master Fund is notorious in shorting against their own position, thus they get trades exhausted and out of their position. Typically Sabby Master Fund primary focuses on biotech sector.