I posted a similar thread in the DL forum. On the DL site they have a box you can check for "Refundable Fares Only." However what they mean by "refundable" is that you can get your money back in cash after the change fee, rather then getting just a voucher. Based on my conversation with a supervisor, DL seems to know that it is misleading and doesn't care.

I asked the supervisor what fares were fully refundable and it took her nearly a half-hour to figure it out.

Pretty disgusting behavior if you ask me.