. A good manager will see the quiet but effective employee or the loud all talk and bluster, but neither are great traits. Employees need to speak up, make their points heard, manage constructive if heated discussions. I manage someone who is technically brilliant and a really nice person, but he is far too quiet, reserved and introvert to get a promotion to the next level which requires leadership. As a manager, we set out milestones, i give hime ownership of projects where he will have to handle heated discussions, i have put him on training courses etc. Slowly he makes progress but he can't yet reach the next level due to being so quiet and introverted. He will almost always have the right answer, the best new architecture, identify the potentially critical nuances in design etc, but he cannot successful defend that and communication clearly then he simply can't be the technical leadership role. Instead he currently gets massive RSU etc. to reward the talent. I hope together we will get hime to the next stage, but really it isn't for everyone. Big difference between an IC and a technical leadership role. People skills become much more important.
The other point when it comes to promotions is these should be evidence based with clear goals and milestones. There should be regular performance reviews from the manager but also evaluations from the individual and also team. All of this should be reviewed regularly, document and preserved in a centralised system. Then when it comes to promotion it should be relatively easy for either the manger or employee themselves to summarize all the previous talent assessments, performance reviews, milestones set and passed.