I recall getting a refund to a different card at Lowe's, although it was a year or two ago. I wasn't trying to do anything on purpose, just had switched everyday cards as I recall and didn't have the original purchase card with me anymore. I actually mentioned this to the clerk, she said "Well, let's try it", and it went through fine. The amount was small, though. And as it was a bit of time ago, it's possible they've tightened things up in the meantime.

I think the biggest issue in trying this (apart from any moral issue) is that of an unconnected large refund. I have to think that would trigger some kind of alert somewhere.

The problem of getting a negative balance refunded is also true, although you can mitigate this by using a debit card for the refund. A signature-based transaction on a Visa/MC debit card should be the same as one on a credit card. That refund would go right into your bank account, from which you could pay the original charge.

Another problem would be with trying to do this on an ongoing basis. If you become a frequent returner, some stores will cut off your return privileges. In some cases, as I recall, such info can be shared with other stores. So you can't necessarily just go around returning forever with impunity.

In general, it's probably more trouble than it's worth, which is yet another reason why this practice isn't widespread.