I can honestly say I learned something from the comment section. I was always taught the .9 repeating was not equal to 1 but separated by imaginary i ... Or infinitely close to 1 without becoming 1.

0.999... / 3 = 0.333... 1 / 3 = 0.333... Ergo 1 = 0.999...

(Or see algebraic proof by @[email protected])

If the difference between two numbers is so infinitesimally small they are in essence mathematically equal, then I see no reason to not address then as such.

If you tried to make a plank of wood 0.999...m long (and had the tools to do so), you'd soon find out the universe won't let you arbitrarily go on to infinity. You'd find that when you got to the planck length, you'd have to either round up the previous digit, resolving to 1, or stop at the last 9.