Jejudo, South Korea
Ever heard of deconstruction?
I don't think they're rules per se but there are conventions. Generally, we can say that philosophers deal with language in a SERIOUS way; that is, they're trying to make a point without resorting to literary devices.
Poets use language in playful (associations, puns, metaphors etc.) ways in order to say serious or playful things.
On sustained study (the kind of stuff Derrida does in topic and in style), these distinctions break down but they still have a practical value, I think.
If you go into a book store and want to read poetry, I don't think you'll be happy with Kant or Hegel, Donaldson or Searle; and if you want to read philosophy, I don't think you'll be happy if you get Byron, Coleridge, Ginsberg, or Ashbery.
But then you never know.