I haven't said anything much on here, but I do play both a paladin and a cleric. What I find funny is that I got a lot more of the "you should play your paladin this way" before Daniella was a champion. I still get it from time to time, but not as much. I can't recall anyone ever telling me I don't play my cleric correctly though. (though I'm sure plenty of people wish she was more of a walking bandaid than she is- they just don't say it
)
But the real point is, even if someone reads a character's background and bio and submission, and their public journal, etc., that still doesn't give a person the right to take that OOC information and put it into an IC form of telling your cleric/paladin/etc how they should be acting. Just because YOU the player read something on LORE, or knows someone of that faith IC, doesn't mean that your character actually knows all about everything there is to know about that faith. "Oh, well my brother's cousin's best friend's wife is a Berylite, so therefore I can apply to the priesthood and I know everything there is to know about your religion and I don't think you're polishing enough stones to be correctly following your religion" Or "I slept with a Xeenite once, so I know exactly what Xeenites are like, and you're just not doing a good enough job" (though I could actually see that as a really bad pick up line...)
On the flipside, though, many very good conversations (and arguments) can happen in game by people of the SAME FAITH arguing or discussing the other's faith or convictions or differences. You may have a cleric of Ilsare who tells the follower that they should not give up on love, or the follower of Ca'duz, who can't believe that their cleric just accidentally stepped on a spider and squished it?! The HORROR! (Lance and Daniella have had countless arguments/discussions on the differences of their faith within the same religion- always very entertaining and enlightening both in and ooc)
The point is, yes, keep it in character. But once again, if you're not playing a character of that faith, you most likely 1) would not really truly know how they are supposed to act or believe- you probably shouldn't know a paladin's code unless you are a paladin, were raised to be one, or were raised by one, etc. and 2) why would you care?
As with most things, please treat people as you would like to be treated. No one likes to be told how they should or should not play their character. It's something personal, and that sort of behavior generally makes people not want to play with you if every time you interact you say something offensive or off base. So... just don't do it. Be nice, be respectful, and if you SERIOUSLY think they've ooc made a bad call, then perhaps rather than saying to them in a tell "dude, you just played your character totally wrong" how about saying "umm... I was just curious... why did you do that exactly?" There may just be something you missed. And as far as really punishing them for actions against their faiths... let's just leave that to the gods.
