I've seen a couple of guys playing right-handed guitars upside down, strung normally, but played left-handed, in the past few months.

I asked one of them, and he said he had just picked up the guitar as a kid, and started playing, not knowing he had it the wrong way round. By the time he discovered his 'mistake' (it's debatable it was a mistake, given how well he could play) it was too late to change, as far as he was concerned.

He was able to produce interesting patterns when finger-picking, because of the 'upside down' strings.