One foremost aspect I see missing in the discussion is: "It depends" It depends massively and that's the main problem. So I'd focus on understanding how that

One foremost aspect I see missing in the discussion is: "It depends" It depends massively and that's the main problem. So I'd focus on understanding how that works with this specific manager M you are concerned about. It will be different with another manager. After that it's detail. Managers are human, flawed, not anywhere near rational (not fully rational anyway), and in some cases crooked or insane. Just like their reports and bosses, kind of? Try and feel out how that manager operates before "doing anyone a service". In particular, it means not relying on the idea that they would reason the same as you do. Because for example, absolutely "providing info so they get to look good, privately so there is no loss of face" will blow up in your face with some managers. Even if it's to the detriment of that manager. In some cases, it will be even worse than this because that manager will be well ahead of you and already have their own plans in place for their own future. In a case like this it's not even necessarily possible for you to imagine what reaction you might get. To be fair, there is a general plan available for you: Cultivate a network, keep your resume in front of people. Then you can be bolder.