Rainbow Mage
Lib Democrat/Agnostic/Epicurean-ish/Buddhist-ish
This isn't necessarily true. Atheists Buddhists, within the Mahayana tradition at least, would disagree. Reincarnation is part of the doctrine of samsara, although most Buddhists would call it rebirth. And the higher planes, as well as the lower ones, are part of the Abhidhamma, accepted by all branches of Buddhism. I'm not sure how you got to where you believe atheistic Buddhists would reject these ideas.
I have met many Atheistic Buddhists who reject the idea of higher planes especially. Also for an Atheist Buddhist to accept the existence of higher planes, do any entities live on these planes? If so, what are these entities?