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?

Yes, which on the one hand is odd - he's just restarted his relationship with Catherine Sakai, he's got a best friend in Garibaldi and a new friend with Delenn - but on the other, if you see Sinclair as a person in transit - his old self got broken at the Battle of the Line, and he's been trying to avoid the question of who he is now since - not so much.