Well, in Luna Eclipsed, Luna's shouting is because that's how royalty talked in Equestria 1000 years ago, and even though times have changed, Celestia doesn't tell her.
This is kind of stretching it and Celestia isn't the only one to blame but no one bothered to listen to Twilight when she thought Cadence was acting strangely. When Cadence acts like a drama queen, the other ponies and Spike ignore Twilight and try to cheer up Cadence while Celestia walks by and tells Twilight that she has a lot to think about and of course Twilight was right all along. You'd think that any suspicions Twilight had would be plausible since she correctly predicted Nightmare Moon's return.