What are the rules exactly?

[Khedrac]

My understanding (I am not a mod) is:

1. You can discuss any religion as it pertains to a game world (but see below).{I wouldn't say this exactly. You can talk about the fictional version of a religion, but you can't talk about a real world religion, even if it pertains to a game world. - Roland}

2. You cannot discuss any religion (fictional or otherwise) as it pertains to the real world.

For example, back in the day Imagine magazine published a write-up of Sobek as a deity for AD&D, basing it on the historical Egyptian deity.
It is legal to discuss the ramifications of the class abilities.
It is legal to discuss how the worship of Sobek works in your campaign world.
It is not legal to discuss whether they captured the real religion accurately.
It is not legal to reference the real world when discussing how the religion works in your campaign world.

There remain grey areas - if your campaign world is Earth, they you have to be very clear that this is your version of the religion and Earth, it is not the real world, and tbh it is probably best not to post here at all - as any reply would probably break the forum rules. This gets easier the further your world departs from reality as it becomes to tell the worlds apart.

So, with regards to your specific question, yes you can discuss the play-ability of the Levite Priest and the Saint base classes on the forum, but do not reference the real-world when you do so.

Same goes for politics.