I want to know if it's dangerous for kittens to be playing on tables that are about waist height, or on someone's shoulder or head?
I don't know that there is a safe height. Falling wrong from a very low height can have fatal consequences.
That being said, kittens are fairly low mass and their bones are actually pretty flexible. It would not surprise me to hear people tell stories of seeing a kitten fall from 10 feet (3.048 m) or more without any ill effects.
However that is not the same as saying it is safe for a kitten to fall from 10 feet (3.048 m). If a kitten fell from height but seemed to walk away with no lasting effects, I would not worry about it. But I also would not go encouraging a kitten to jump off a balcony or dropping one, except in case of an emergency where the alternative is certain death.
As a very conservative rule, kittens can safely jump down from the same height they can jump up to. Anything higher, i.e. requiring climbing rather than jumping, may be unsafe. Even minor injuries in a kitten that young aren't good and could have lasting effects (and expensive vet bills).
My most recent kitten taught himself to climb up onto my bed, but he sprained one of his front paws jumping back down—onto carpet! Once he recovered, I made him some steps (stacked cardboard boxes) to get up and down safely.