Is being the only remaining developer in a department a good reason for promotion if one does everything that a senior developer would do aside from displaying eagerness, passion, and being popular?
Basically the person does not go out of their way to be friends with everyone at work, but he does handle all of the job responsibilities and workload that would normally be required of a someone in a senior position. He handles all the job responsibilities the previous senior developers had. He's just not socially outgoing. That's not really what management likes to see.
Is that enough good reason to move him to a senior position?