I haven't seen too much of that to be honest. The closest I have seen to that is various parodies of that annoying "meseta please" one. (And it deserves to be made fun of.) Most of these idiots are just copying the porn ones from online and are too lazy to pursue that further. (It's pretty obvious. Most of them have Japanese filenames.)
Now, if you want to get into the category of "harassment", I've observed that making a fuss tends to just egg on the idiot edgy teens that do this. Don't bother calling them out. You cannot shame them because they do not care. Getting a rise out of you rewards them. Just quietly block and/or report. They usually stop or look for another channel to annoy when nobody reacts to their childishness.
It's just like little billy cursing on Xbox Live. It's pathetic. Don't make it worth your time and energy.
Edit to add: I suppose I should mention I show up to concerts fairly frequently, and that's where the trolls like to go. However my screen is mostly clean. I do still observe people fighting over the symbol arts in-game, which is how I know they're still getting spammed.