For anyone who plays on a server where this isn't a problem and is blissfully unaware, the new RMT strategy to annoy the living **** out of you is to send you a spam tell and then immediately send a Friend request. This prevents you from just Blacklisting the RMT spammer, you have to open your Friends list, scroll all the way down to the bottom, click on it and Decline the request, and only then can you add to Blacklist.

What needs to happen is that you should be able to add to Blacklist whenever you want, and the game will automatically remove the player from your Friends list if you do that.