> It's sad that pairs like true/false, good/bad, first/rest, and left/right are unequal length.

You're just matching them wrong. On/off and yes/no may look unequal, but what about yes/off or on/no?

This reminds me of all the (fun) times I had coming across “enable toggle” and “disabler enabler”.

Bonus points for taking “YES” (looking at you FreeBSD) or “1” or “ON”.