On my channel, probably back in mid 2008 when I had some of my old piano videos, one of which is a quick recording. I don't really have trolls commenting but just trolls giving my videos 1/5 stars. (this was way before YouTube switched over to the like/dislike rating system.) I personally just disable ratings if things are pretty bad
Nice job! It seems like a good anti-troll measure, give them what they least expect and when they feel that they aren't getting the satisfaction that they expect, then they leave/die of boredom