My understanding is: Everyone is free to post in every board. If the topic has to do with Christianity then put it in the Christianity forum. If the topic is controversial, you can probably expect to be challenged but civility is still the rule.
I think you can also place topics related to Christianity in Belief and Spirituality, Esoteric, New Age, Comparative...depending on what the topic is. Depends on what kind of perspectives you hope to draw I would say.
It's a work in progress.