Blacklisted Char Can Still Send Tells?

I blacklist gold sellers because they often send 2 or more in fairly short time, they repeat the offers from the same toons fairly often, and it's annoying as all get out.

However, I got a tell from a seller just now, and when I went to blacklist him, the game told me he was already on my blacklist. Then how did I get a whisper from him?

I checked the list, and sure enough, he was on it. How did he bypass it? Once I opened the blacklist, I then no longer had the option to add him to it (even though there was room on it).

Picture 1: Error - "Player is already blacklisted"

Picture 2: Showing the blacklist

That is genuinely worrying. I hope they haven't managed to elevate themselves to GM status & thus force tells through. If they have then we have a lot more than spam messages to worry about. =(