I don't know anything about it, but I know that when pretty much anything in life seems too good to be true....
I doubt NerdWallet is offering this service purely out of the kindness of their hearts. Obviously there's something in it for them. So you have to figure out if what's in it for them is ultimately going to be costly for you. Maybe it is, maybe it isn't... but I do know that if this were simply a sweet rewards program with no catch, a lot more people would be talking about it.
Oh, I hear you... but there ARE those services out there that say something like "Hey-- the company offered us 6% commission, so we'll split it with you."
Otherwise, I don't doubt there's an advantage for them at all. My question is, has anyone done it and what do those 'shares' (Discounts) look like?