Well you are wrong here. Previously in this thread it is confirmed that the letters are sent to random characters, NOT players
That's not how I read it. It is IC - meaning that it is 'is this IC message vulgar' - but it is not IC like 'does your particular character happen to find it vulgar,' because those are two different standards. The latter is totally subjective because I can't tell you how vulgar your character should be, but the former, while not absolute, is at least open to evidence and argument, and we even have some basis right in the text, i.e. 'don't act like a peasant.'
The challenge is that, no matter how educated we are today in 2013, most of us talk like peasants.
As to your definition of vulgarity, do you believe nobles ever leveled insults at others or only ever treated others with full respect?
Of course not. 'Not vulgar' doesn't mean 'nice,' just as the in-game message says - you can (and should) offend your enemies. Doing so while not looking like a peasant is the job.
In addition, you CAN insult a noble while still showing them respect. That's the point of letters like mine.
You can do this but it is harder than most people think, because to be insulting but not vulgar requires effort and wit. I'm not setting myself up as an example here, or you as a counter-example - on my good days I've come up with a few good lines but it is legitimately tough to do! To walk into a noble court in 1300 and insult someone else in the court would be viewed as bad manners. To do it gracefully and make the other guy look bad (presumably the point of a good insult) you had be more inventive than sex and beer jokes, which, as has already been pointed out, is what your letter amounts to.
I've seen a lot worse but if the point was to insult while showing respect, I'd say (along with whomever agreed in-game that the message was vulgar) that you missed your mark. I'd have a very difficult time re-writing that letter to not be vulgar because the whole premise of the thing is sex and rape jokes, and you have to be a lot more clever than I am to get away with those without being vulgar.