This is a sign most anyone in the States can see in any retail business. In fact, it's so well known that most people take it for granted. If I own a bookstore and you as a customer start screaming at other customers or employees, I can ask you (and have the police enforce it) to leave. Sure, you can sue, but it won't hold up for a second in court. Same thing for a theater: talk too loud during a movie and you will asked to keep it down, or leave. One pays $7 at the theater ticket booth to be entitled to watch a movie, not to act disruptively. However, act sensibly and everything should be great.
An online game is really just a business with clients, so the same rules apply. Act within reason and there should be no trouble, but start to become disruptive to the online community and you should be asked to leave. In many of the text-based MUSHes out there, there is a known standard by which players are expected to behave, and it's called being in character(IC). In fact, it's placed in the help files and all new players are asked to read it before playing. Act Out-Of-Character(OOC) and you can ultimately be barred from playing should the offensive behavior be severe enough, or repeated often enough.
I saw an article about online behavior in a recent computer gaming magazine, and this was their argument. To me this makes a lot of sense. So, paying $30/month to play AH doesn't give one the right to be offensive or disruptive, or OOC. HTC, this may be something to consider once AH is up & rolling for production. I seriously doubt that it would create any loss of your customer base. Telling people to leave a bookstore or a restaurant for offensive behavior generally doesn't affect the business adversely, and in fact, not doing so sometimes results in the loss of good customers.
Just something to think about...
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129 IAP VVS RKKA