[kccqzy]

LaTeX doesn't have enough information about what your notations mean. You can very well write nonsensical formulas that look pretty in LaTeX but are absolutely meaningless.

[bingerman]

I wish I had read the texbook or something similar sooner to gain knowledge like this. Used latex for years without knowing the basics and I regret that a lot.

Also, (v)phantom and smash are something I really should have learned before all those fancy packages, nowadays I'm mostly using context anyways.