:D That was the reaction I got in game too. Except, I wouldn't know if you tried it or not. So I couldn't go "Haaa got ya, sucker".
If I was really trolling, I would have to tell people in game, watch for someone suddenly go offline and then go "ha ha, I got you". The payoff just doesn't seem worth the lulz.
Anyway, it does work. Try it or don't, I am just offering free information from the GM.
For me - it worked. I don't know how WoW system files and stuff work, but when I logged back in, the filter was still off.