I'll speak up as one of the proponents of the, "You should believe nobles over minor functionaries" camp.
The problem arises in instances where the game itself is ambiguous. I recall a case in PoZ where my character was at odds with one of Tim's characters over the situation surrounding one of Perth's characters' controversial actions.
Long story short, the early RPs were contradictory: many characters made totally impossible statements about what happened, or RP'd drastically different events. Characters claimed to hear and see things from miles away, and alleged weather out of line with the season, etc. And the game only states a small amount of information: yes, it's undeniable that so-and-so was arrested. But it is quite debatable what the exact details were. And in a confusing situation with lots of IG reports coming out (such as a religious uprising followed by arrests follower by upset peasants), the game can sometimes create contradictory reports, or reports that are at minimum very, very hard to reconcile into a coherent narrative.
Game mechanics do trump RP. But, IMHO, game flavor text only kind of trumps RP. And when game flavor texts don't always perfectly align, and then players trying to retcon their actions to fit those flavor texts all tell different and incomprehensible stories...
I choose not to trust the peasant scribes. I'll still to the word of the nobles I trust.
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To a related question I think was asked: is it meta-gaming to forge the trappings of message details, like timestamps and formatting and such. IMHO, no it's not. Think of it as, IG, our characters forging the seals on the letters and the signatures and such. There are non-textual clues to a letter's validity, we simulate them by developing our own non-textual (or at least para-textual) clues.
