To valinors sorrow,
I don't think there is any specific principle separating the two. The Religion category tends to have more "Holy Book" references and questions. However, I think most posts could or should be in the Spirituality category. I prefer to look @ my Religion more as Spirituality.
I don't know if most do though. But you are probably safe. And I don't think there's any "rule" either.
Just a thought. I know I'll probably be here a lot!
Cheers
