But Commanders are NEVER referred to as Captain. It simply wouldn't do .......
...... Quite apart from the fact that the rank of Lieutenant Commander was only instituted in March 1914 although, since 1875, Lieutenants with eight years' seniority had worn two and a half stripes to distinguish them from their more junior colleagues. It probably won't come up Chez Bloggs, and many Lieutenant Commanders don't like it, but rather as Blacksheep points out, a Lieutenant Commander is therefore effectively a senior Lieutenant, whereas a Lieutenant Colonel is effectively a junior Colonel.
Some people feel being a Commander is actually much more fun than being a Captain since, in civilian life, most people have no idea whether a "Captain" is a Captain RN, a Captain in the Salvation Army, or the skipper of the Gosport ferry, whereas they seem to know, perhaps thanks to Ian Fleming, that a "Commander" is a senior naval rank, or, thanks to the plethora of police programmes on TV, an even more senior police rank equivalent to an Assistant Chief Constable!
B-Day -6 and counting ......
Jack