Stupid NES Tricks – Screen Wrap Detection

That would work, but that means branching to handle the left/right difference. The author mentioned that he wants to avoid branching to maximize performance.

Avoiding branching is still relevant on modern machines when optimizing hotspots, and even moreso as cpu instruction pipelines get longer.

That's correct, however that would involve some branching. In theory you could do a bit masking trick to use the same code, but that would end up much more complicated and slower than the presented eor hack. That being said, I'm pretty sure that your idea could easily be done on a more modern processor.

Depends on the semantics of the processor's carry flag. That sounds plausible. But if you have to know whether the delta is positive or negative, you'd lose much of the speed benefit of the hack.