But preaching is a crime in Keplerstan, the game mechanics simply don't recognize that.
But preaching involves commoners. You would tell a noble that he has no right to speak to a commoner? I was under the impression that a Noble can do whatever they like to commoners. An infiltrator's actions are against the nobility. Be it changing road signs, attacking a noble or stealing gold. Now, if a priest were to cause the commoners to rise up against the nobility, that is a crime and it can very easily result in the priest getting sent to jail.