Clarity, literacy, unpredictability, original humor, and answers that impart information, helpful hints, directions out of a labyrinth (viz: IRS questions) and the sense that we are a community and not a private club, frat house, beer hall or locker room.
Srmorgan, Cwlbur, johnpowell (most of the time), Tali, sndfreQ come to mind as people whose questions and answers I always admire (and understand on the first reading.)
I am omitting some people..sorry, but I don’‘t know who has left the bldg.