[jrockway]

I've been on promotion committees where it was clear that the manager didn't support it, but we promoted the candidate. I feel like most of the memorable discussions in those committees were figuring out how to give the manager feedback on how bad of a job they were doing.

I agree that you're basically screwed, especially L3->L4, if your manager isn't actively counselling you on how to grow your career. You obviously don't have enough experience to do it on your own at that point, so you are at their whim. Even when you do have the experience, if you don't have a good working relationship with your manager, you're in trouble anywhere. It is ultimately going to be them or you, and you are easier to get rid of ("he took another offer" versus "everyone thinks your manager is a jerk, so we fired him, oh by the way in the meantime your career is on hold while we figure out what the fuck to do please keep showing up").