- I haven't read the fic in question, but I have a question: Dexter concludes that Luna is the stronger of the two, since her portfolio encompasses the moon and stars. However, Celestia was able to move the moon and stars for a thousand years seemingly without help from her sister, so shouldn't the fact that she was able to pull double duty mean she is the stronger? At best, you might conclude that Celestia might be drained from doing so much for so long.
- It should be noted that he believes either of the sisters moving any celestial body was propaganda and did not even know the full history following Nightmare Moon's banishment. Also as Dexter said moving all the stars in the sky any noticeable distance would require orders of magnitude more power than moving the sun around the planet so even if Luna couldn't do both any measurable difference in power displayed by that one event would be tiny.
Headscratchers / Dexter's Lab: Equestria