@Luzipher: Some Japanese art styles use pointy teeth to further express anger of various forms. But for some reason this artist gives everyone pointy teeth regardless of the mood. If an expert on this matter would like to chime in, that'd be great.
Its a way of defining a scene on a fictional character. Realistic pony teeth wouldn't make much sense to 99.99999999999999% of the audience and most scenes require a high degree of facial expression.
A good example would be # 11 : In the top left panel, the white pony is shocked but since her hands/hooves are occupied with holding Spike, the artist needs to express her shock (almost) entirely through facial expression, thus teeth.
Similarly in #8, the image is obvious dominated by the pony's ass, but that also means the immediacy of the scene has to be defined by her facial expression.