Came across this blurb on AC's website today: "If your ticket is non-refundable or refundable with a fee, please note that when changing to a lower fare, any difference in value is forfeited."

I don't quite see how AC would enforce the latter scenario? If my ticket is refundable with a fee, what's to stop me from refunding the ticket, forfeiting the refund fee, and purchasing a new ticket with a lower fare (assuming the fare difference is greater than the refund fee)?