Weren't Sheridan and Lockley Captains and not a commanders?
I was wondering if somebody was going to language lawyer that. But when you're talking about "commander of a station", it's little 'c', not big 'c'. Just like the Navy uses 'captain of the ship' for whoever is in command, regardless if their actual rank is Captain or not.
Army/Air Force bases have commanders, but those branches doesn't even have a Commander rank. The closest thing would probably be a Lt. Col as they're both O-5, though IIRC even Majors have been known to command smaller bases.
Actually, that quote is from Ivanova in Sleeping in Light, speaking retrospectively, so canonically true.
I don't remember anyone calling Sinclair B5's "last" commander although it is possible. I confirmed in the Pilot the narrator referred to its "final commander" but didn't name him so technically wasn't incorrect. Also, that narrator was Londo, an in-universe canonically unreliable narrator.
The line from the pilot is what I was thinking of. True enough about Londo, though the pilot was retconned in several other ways as well, so it's already less reliable.
Come to think of it, I'm not sure if I've ever watched Season 5 all the way through. I've seen the first 4 a bunch, as well as Sleeping in Light and some of the movies, but that kind of covers the big story arc and most of season 5 seems superfluous.