Does non-combat damage affect Commander damage?
Per the official rules on mtgcommander.net,


  If a player has been dealt 21 points of combat damage by a particular Commander during the game, that player loses a game.


"Combat damage" refers only to damage dealt in combat as a result of attacking and blocking; direct-damage abilities don't count. Note also that Obzedat, Ghost Council's triggered ability doesn't deal damage: it simply causes your opponent to lose life.