I would be confused if 1/2gt^2 would mean anything but 1/2 g t^2 and 0.5 g t^2. 1/3x in isolation may look a bit unusual, but with context the choice between 1/3 x and x / 3 may actually convey additional information, information about the structure of the calculation. Manipulating an equation into some kind of normal form may lose information.