First of all thank-you for your question. I understand your concern and have seen the downside of this type of behavior on flyertalk.
I think your question is a two part question, because i see two seperate issues in your question. The first issue is sarcastic comments and the second is the rudeness issue.
The difference in these two I beleive is important. Sarcasm is often a way in which many people communicate especailly when responding to a question that seems so obvious to them, has been asked many times before, or is something that community has turned into a joke on its own. (thought that came to mind was the warm nuts in the United forum.) Sarcasm is fine, at least from my point, as long as the sarcasm is clear. Rudeness on the other hand is a different animal. In a community as large as Flyertalk, we cannot legislate or even stop folks from being rude. It is human nature. However, what I think we can do is try to encourage responsible behavior of our members. Further, rudeness takes away from the sense of community that is flyertalk. A new member (either to FT or a forum) can easily be turned away by continued rudeness by members. If this happens then it can become a problem.
So to answer your question, I don't know if we need a sticky to remind members to be nice to each other. I know that the TOS prohibit attacks by members against other members. So do we need to consider a policy against rudeness, i am inclined to say not at this time. I think that the members of the forums in conjuntion with the moderators can encourage good behavior and limit rudeness without having to have the TalkBoard step in. however, if rudeness becomes an constant issue, then i would say that i would reconsider my position.
Again thanks for the question.