I think it would be worth adding mention of the expected currency for sales in the .ca sales "rules" thread.

As a seller, on more than 1 occasion, I've posted prices assuming that unless specified I'm listing USD as all other sales are done (I mean, do we pay euros for co.uk?) then, ultimately when a buyer sends CDN and the variance is actually larger now than in recent months, it would help to have a ruling to refer to in the .ca rules section

all sales in .ca are assumed in USD unless otherwise stated or vice versa...just as long as its said.