I think that question would take a book to answer, and I'm not aware of anyone having written that book yet. (I'm certainly not the right person to write it.) It's not that hard to work this stuff out for yourself, but…

  Trust not your self; but your Defects to know,
  Make use of ev'ry Friend——and ev'ry Foe.
    A little Learning is a dang'rous Thing;
  Drink deep, or taste not the Pierian Spring:
  There shallow Draughts intoxicate the Brain,
  And drinking largely sobers us again.

You can completely destroy a community if you've found some of the fundamental principles, but not those which counterbalance them. (And you don't even need a formal position of power to accomplish this.) It's this partial understanding that I was referring to, in that last paragraph. In the absence of a good book, I don't think a moderator can learn these things without good mentors, a rogues gallery, and many mistakes – but those mistakes can prove fatal without good mentors to fall back on.