Whether or not Blizzard actually does anything about it, public NSFW RP is against the rules of World of Warcraft. Hell, even TRP’s are no longer considered ‘safe’ and are considered by Blizzard to be actionable depending on their content (and with an update to one of their API’s a while back, they can actually see what one’s TRP3 content is).
Many people can tolerate NSFW RP in public spaces, but because this is against the rules of the game itself, you are free to ticket/report these players for violating the code of conduct/terms of use. At this point, its not about the story, character, etc. etc. Its not about the Roleplay…its against the rules of the game itself, like it or not. Report, send their TRP to Blizzard via the in game tool featured on the addon, and ignore if it bothers you. And to all of the NSFW RPers who do that sort of thing in public spaces? Not saying anything will happen…but know that you can be muted or even banned for this behavior. Party chat is considered fair game, as long as it is between consenting individuals, so I would recommend using this to mitigate the potential risk of such behavior.
Again, this isn’t RP etiquette, this is a violation of the very rules of World of Warcraft.