I'm a couple of days late here but I know a lot about this so i'm going to chime in. You can get banned from using the service and investigated for fraud if you accept funds from a stolen account. I work for Interac and this scenario happens all the time:

• Scammer gets access to bank account via any number of ways. Phishing scams, stolen device etc
• Goes on kijiji and tries to buy something expensive, insisting that EMT is used for whatever reason
• Scammer sends EMT on the spot using the stolen bank account. - Seller is unbeknownst while it's happening because the transfer worked and all seems legit
• An investigation is opened by the person who the bank account actually belongs to and it gets traced back to recipient. Best case scenario you're banned from using EMT service worst case you're investigated for fraud.
  

It's not really worth the headaches to use EMT to buy and sell stuff online. Plus if they're this insistent to use EMT over a cash or a cheque isn't it a bit sketchy?