If staying in lane would help to disperse the traffic jam, there would be a point to keep forbidding passing at low speed. It doesn't. It isn't even safer, especially when one views the amount of head-tail collisions at the tail of the jam.... I wouldn't want to be there on a motorbike when someone overlooks that traffic ahead is stationary. Passing the rows of cars with a low overtake-speed can only help. Emotions like "if I'm stuck in traffic, they should be too", don't help. Overtake speed MUST be low, though, "vollidioten" that race between rows should receive hefty fines!
Quelle: Passing traffic-jams has no negative side-effects.