@Crystal Neighybánya
The reason is that the writers really want you to sympathize with Starlight, so they go out of their way to make sure that you in some way always feel sorry for her or want to root for her, at least that is their intention. So to do so, remove any element that might make her look bad or unsympathetic, such as being snarky or dismissive as that makes her look ungrateful for her new chance at friendship, and thus not worthy of it. Of course because they are trying so hard to get you to like Starlight, it doesn’t stick with everyone since some aren’t going to be drawn to the character after her mishandled redemption.
I half agree with this. I think they’re trying to make Starlight likable because they want her as a role model, not as someone you would feel sorry for. If the character was sarcastic, cynical, or out right makes fun of other characters, she would not be an ideal role model for the little gurls.
Which is strange because there are characters on the show like RD who gets away with it most of the time and Rarity who is a more rounded character because she has a fair share of negatives and positives to her character.
I want to see an episode like Every Little Thing She Does where Starlight smiles at the magical chaos she causes and when Twilight scolds her all she says “Ah, yes… Friendship. I understand now.” And then turns around and leaves laughing to herself. Lol. Makes her look like she has mental problems consistently with her back story.