Originally Posted by eigenvector

Oh, I agree with your reasoning. But I don't think it prevents AC from trying to weasel its way out of compensation. I think we know the argument AC might employ here: OP was offloaded before new pax were confirmed, therefore there were never more pax holding confirmed reservations than the number of seats available because AC unconfirmed OP's reservation, therefore Rule 90 doesn't apply. This is of course a rubbish argument since as the CTA has confirmed an airline can't just unilaterally unconfirm someone's reservation at its own convenience, but that doesn't stop AC from using it anyway.