This is what I believe, this is a mix of a bunch of diffident theories. The text we see on the poster, and elsewhere is what they normally wright in.
Think of it as stranded Equestran, are latten alphabet wood would be like there cursive, used in formal events, or jest to make a good impression. The squiggly text we see spike using, and on the cake is jest a faster way of wright, and is possibly how there type writers work with only 2 keys.