alright, after purchasing some TMSC on the DEx yesterday, I tried creating then canceling (by posting a new offer with amount 0) a sell offer with the address 1B4dzdSTt8p1qfMba4MTPUvABDXDYTHT2S
on mymastercoin I see only the (correct) TMSC balance
In mymastercoins when a sell offer is cancelled it will be removed from the sell offer listing. I'll probably add a view previous sell offer so that it can be verify as cancelled.