BlackFlame should not be a choice in character creation. It should only be a choice in character development. It confuses new players to much.
The 'whispers' crowd are not BF followers. Once you do the quests, you will understand.
BF followers do not try to hide away from 'normal' people, as LigH implied. They blend in with normal people. They appear to, and may even follow the other gods.
BF followers are not "up to evil" all the time, nor do they spread chaos. They just follow orders they are given. Some of these orders may be very bad, like burning down and orphanage. Some of these orders may be very good, like helping build an orphanage. Every order to a BF follower is like setting up a domino in a vast cascade. It does not matter what color each domino is, as long as the end go is achieved.
My advice to play a BF follower is this: Don't. Play a follower of another religion, but in the back of your character's mind, they know it is all an act. You are a sleeper with a normal life, playing a normal character, waiting for orders. You don't know what the end goal of you masters are, just that their orders MUST be obeyed without question.
Who am I? I am the person who wrote half of the BF quests and most of the books (if they are still there) in the BF library. The real quests for BF (not the whispers ones) do not present an obvious answer. There is always a choice to be made, even if you don't see it.