Again I don't understand the issue with the words :dirty" and "brown" in and of themselves. Unless they are being used in a weird context.
That being said; it's common on all these sites to see models breaking the rules. Sometimes they never get caught, sometimes they do, in time. Doesn't ever mean anyone should do what they do. Definitely familiarize yourself with the rules, and don't concern yourself w others as much. If they get disciplinary measures that's private between them and the site, so you'll never know the details of that anyways. But, yeah, don't ever base what you do off of what you see other models doing. This is a high turn over industry.