I heard that a well run airline in India manages the fuel issue very well. They've used historical data to calculate average vector/hold times at all their destinations and included the extra fuel in the flight plan. If pilots carry extra fuel they have to put down a reason. The company doesn't argue that the pilot-in-command has the right to put on additional fuel, but the company has the right to ask the captain to justify the uplift. Extra fuel is rarely taken. There aren't many diversions due to the accuracy of the flight plans.
Comfort fuel is a state of mind in my opinion, especially in other parts of the world were an alternate is always required. I know that I carry too much fuel, but I'm selfish. I don't think it helps the company in the long run.