If you want to improve your odds against a mis-wired outlet/plug, you can treat both of them as equally scary with something like this:
That’s intended for the differential inputs of an energy IC, so you might need to tweak appropriately for your needs.
In the lab, when working on something with “dual supplies” you really need to be careful you’ve isolated everything before you dive in to probe/debug. A trap is to disconnect the USB (or PoE cable in my case) see all the LEDs go out and think it’s safe to pick up the board and start adding scope probes.
For additional security against concentration lapses, you can wrap both sides of the board around the divider network in a 3D printed safety cover:
