Whereas some in this debate seem to be operating on the basis that religion
> is primarily about supernatural beings (or Gods, to put it more simply). I
> thought there were religions that didn't even have Gods as such?
>
> Until we clarify these basic premises, it will be hard to even understand
> each other's arguments.
>
You're right that "theism" might be a better term. Non-theistic religions, like most of Buddhism and some sects of Hinduism, also tend to be the ones that don't fall back on "good" and "evil" per se. Despite the misrepresentations you'll see in Western pop culture, karma really isn't about moral judgment. It's more a matter of cause and effect.
I'm by no means a scholar of comparative religions, but the only one I know that combines non-theism and moralism is some Western atheism! If there's another, it will also annoy me.
-- "Hige sceal þe heardra, heorte þe cenre, mod sceal þe mare, þe ure mægen lytlað."