Okay, so in the First 2 Episodes I think it was part 2 where this actually happened when Twilight drinks the potion Zecora gave her (that white potion) she goes back in time/views past events shouldn't Celestia and Luna be speaking in Canterlock?

Okay, well I guess the Celestia vs Nightmare Moon can be excused because they weren't addressing each other as Subjects but the time when Luna and Celestia are trying to get rid of Discord they wouldn't be regrading him as a subject right?