it's interesting that each and everyone addresses Sinclair as "Commander" when he's in his own head, including Garibaldi, who rarely does so in real life

I agree it's an interesting point - though I think Garibaldi *does* usually call him "Commander" in official circumstances (and he does, at the end, when they're trying to talk him down). In personal conversations he quite often calls him Jeff, but not always.

It's also kind of depersonalising, isn't it? People don't relate to him as an individual, but as his job. So it suggests his overly-strong focus on his job, but also perhaps that he feels quite isolated at this point?

I expect Koenig would have improved this episode, but I agree: B5 without Bester would have been a much poorer place!