I can understand team orders in the context of a fight with another team. I didn't get it when the team didn't really have much to win from them, just for the sake of favoring one driver. MS would have beaten Barichello anyway in the long run. What was the point? It was nice to see that in similar circumstances Mercedes allowed it's pilot to fight. And proof stands the fact that Rosberg actually won. But I suspect the reason they keep Bottas now is that he is close to that level where he helps the team enough in the constrictor's championship without creating too much internal fight. He's not good enough to fight for the title and nice enough to just get out of the way when other teams get close. He's close to the perfect no. 2 driver.