PnP, today, there were apparently very few Canadian buyers active and trading through the US exchange, thus, the early sellers today found very few buyers.  Last Friday, the converse was true, Canadian buyers were in the market, while very few US sellers were selling through the TSX.  I'm not sure most US buyers even have the knowledge or ability to route a trade through the TSX on a day when the US markets are closed. 

When both exchanges are open, I think the brokerage houses we place our trades through may route them either to one exchange or the other.  

Tomorrow, a similar situation as today awaits, however, tomorrow, the price may be at a level where the remaining US shareholders who want to take a tax loss don't want to sell.  Hard to say.  But if the volume is fairly light tomorrow, and should the price fall some tomorrow, my guess is Canadian money will be looking for a bargain price on Wednesday morning.

If the stock is off a bit tomorrow, then, I'd look for some late support from those predominantly US traders who will consider buying thinking they can sell Wednesday for a small (but very quick) profit.  But that will be small time stuff.  And with Poet, small time stuff can lead to relatively large percentage moves.

In any event, the volume has been light enough lately to conclude that the recent high percentage moves are of materially diminished importance.