Yeti....I gotta employ my favorite expression on that one and say "meh".

You are absolutely right, shares held in a marginable account can be loaned out and dumped back into the market....the shareholder doesn't even realize they've been replaced by a digital IOU.  Likewise the investor buying them a second time, he/she doesn't know that the shares that have been bought, that they're actually borrowed shares.

But with 50 some odd million shares in the public float.....I don't think its possible or even realistic to expect enough of them to be held in Resistered Accounts like RSP or TFSA accounts....that don't allow margin.

800K or so short against 50 million....again, "meh".  If those selling RVX short are determined to do it, I have little doubt they could locate at least a few million if they wanted.  That's assuming the rule on "positive determination" is in play....if its MMs going short, they're exempt from the rule if engaged in genuine MM activity.