Some people believe that "absolute" polarity matters -- that is, a
compression (rarefaction) in the original sound should be reproduced as a
compression (rarefaction). I experimented with this 28 years ago, and never
heard an effect from simply flopping the polarity of both channels. Even if
it were audible, there are no industry standards for recording polarity.

All that matters in practice is that both sides are wired identically. This
gives maximum bass, and guarantees that mono components will be properly
centered.