Question

How are moderators chosen to be, well, moderators?

Answer 1

Moderators are chosen based on how well they interact with other users on the site.
They should have good level of maturity. They have squeaky clean abuse records, tutor and provide solutions instead of just giving answers,in short, make sure CoC is enforced.
They tend to be experts in their subjects so they can give right answers and correct wrong answers.
But it is in big part based on participation, courtesy and respect. The site administrators pick mods.

Answer 2

Cool cool :)