I've got some post and tube wiring in my house, and I was told that if I
upgrade the electrical system at all, I have to rewire everything to
current code standards.

The only way to avoid that requirement, AIUI, is to paint arrows
indicating the direction of electrical flow on the old wires, every six
inches, with Testor's plastic model cement, in Chevy Orange.

The problem I'm having is that I can't figure out whether to paint those
arrows using the electron flow version of circuit theory, or
conventional current. Anyone familiar with the NEC on that issue?