EDIT: In reference to ^ban^'s post below, I'm aiming the first & second paragraphs at Bedwyr, the rest is to all.
I'm not quite convinced on religion. Whilst I admit that what you said
should be what a noble thinks, you have to think about players. Playing religion how it's supposed to be simply isn't fun to a lot of players, trying to force it down their throats with "you're a noble, nobles follow religions".
I'll certainly agree on not being socialists, however only to the extent of "don't hug commoners". If a noble wants to invest in the lower classes, make sure (s)he only does it for those with a bit of money - for example: build schools for the children of wealthy merchants, open a library for those who can 'donate' gold to the cause.
Thinking about it, what might be best is making a list of what you can't do instead of what you can do. Otherwise, we risk prescribing what many nobles on the continent acts like. In which case, a list like:
- Don't like commoners/peasantry.
- Don't deny the existence of God.
- Don't be lewd, that's for peasants.
- Don't copy/paste letters, you can write.
Everything else is up to the player, which is what makes the game
fun.