Explaining Princess Celestia v. Princess Luna · 1:52am Dec 15th, 2016
I had an inkling of why, perhaps, the naming is uneven between the Two Sisters, which I believe I shall use henceforth.
You see, when Rana* and Luna took over the celestial motion duties from the Unicornian Conclave after the move to Equestria and reconciliation of Hearth's Warming, they were both elevated, to become the Princesses Celestia(l). For the first muchness of their reigns, they were distinctly styled by their other names and titles. However, once Luna fell to the Nightmare and was banished, and stripped of her title consequently for rebellion, there was only one Princess Celestia, and, through one cut corner or another, after a thousand years, her distinct name was only rarely used, mainly in formal treaties. To most, she was just Princess Celestia.
*Hausa for the Sun. I chose it for parallel, twinlike sounds. Pick another word if you so desire.
Now, on Luna's return, everyone was used to calling "Princess Celestia" just that, and she does try to avoid disrupting her little ponies' lives when she may avoid it. Thus, she granted her sister the title of Princess Luna, with most of the responsibilities and duties that she had had before, governing the night sky, dreams, and so forth. However, having failed to grant her the actual reigning title of "Princess Celestia" she retained technical monarchy, and Luna need not trouble herself with signing any of those new treaties…
