When you go to use to book a ticket using this voucher, the website gives a vague message about maybe not earning miles, upgrades, or MQMs. However, my experience is that you will earn MQM's, miles, and upgrades (if applicable). It is really just another form a payment to pay for a airline ticket (and is treated the same as a credit card payment). I guess this could change down the road, but no one has reported a real life instance of this.

Happydad