Ethan Blanton on Nostr: Inputs are approximately the same, in reverse -- they're much higher impedance than ...

Inputs are approximately the same, in reverse -- they're much higher impedance than the supply voltage, so any minor difference in supply voltages will be dropped across the input impedance. If you're feeding output-to-input there'll be no problem at all, and rail-to-input (while less ideal) shouldn't be a meaningful problem as long as the supplies are nominally the same. If you check the data sheets, usually the high input can be a smidge over rail.