Apparently in some circles of the Internet, ""I'm too dense to get the hint about the filter" Pony" is somehow associated with mental retardation (I never got that idea--I only ever associated it with the wall-eyed look or with having a "brain fart"). So that name created a major drama fest over whether the character was discriminatory, whether that particular slang term is discriminatory, etc. There has even been drama over portrayals of the character with crossed or un-crossed eyes! Hence, her name is censored on the Arena to Drama Pony. She just causes all sorts of drama and flamewars wherever G4 and FiM are discussed.
I like the character, myself, but I do understand and respect that she can be a bit...controversial.