[crawfordcomeaux]

Would it be possible to use - 0 & +0 in useful ways, like determining "direction" of previous operation? No clue how that could be useful, but I'm betting there's a use case out there.

[cmrx64]

Yes! Although I'm not sure if it would ever be useful for integers, it's vital in floating point: https://people.freebsd.org/~das/kahan86branch.pdf