My archetypal staff engineer is Wernher von Braun, father of Saturn V. The quality he demonstrated:

  - Breaking ground. He turned a seemingly impossible idea into reality. 
  - Getting substantial breakthrough in each iteration. 
  - In the trench. He was the designer of multiple rockets, and he was the person who solved tough engineering problems and pushed the boundary of rocket science. 
  - Leadership. He knew what he had to know deeply and what he could delegate, and he unblocked his teams whenever needed. 

In contrast, the Staff Engineers I see in many companies are technical product managers, skilled coordinators, excellent box drawers, and masters of jargons. They do everything but engineering. You can probably identify them easily as their resumes are full of phrases like "uber technical leader" or "coordinated across 100 teams". Their careers depend on how lucky they are to find an effective team to execute. Mind you, this sounds like my blame, but it's really not. If anything, it's my lament. Those engineers were deeply technical before they got promoted. It's just that sooner or later, the leadership needed someone who could communicate up and down and around. The staff engineers would need to show up in more and more meetings, "align" more and more teams, conduct more and 1-on-1s to build relationships, draw more and more boxes to appease the "stakeholders". Sooner or later they are busy in meetings all day, they are no longer in the trench, and they get comfortable with throwing terms like BERT and Raft and what not without knowing the underpinning theory or implementation in a coherent way. Of course, there's nothing wrong with such roles and they will continue doing well in their positions. It's just that I'm not sure such job would give me much satisfaction.