I don't know for sure... Our subject in-question was a suspect of this behavior, getting seemingly joking insults at them over and over again. The subject however, did not take them as a joke. They told me about it when just two of us were in the same chat room. Before that, I was just playing along to everyone else, but after that point, I stopped it. Later, I also tried to prevent it from happening, since I have been a suspect to this behavior in real life, and I know how it feels like. It appeared that it worked for a day or two, until it began again. At that point, the subject seemingly started to accept it, but I am not certain if this is true or not.
I am also not sure if the subject allows me to talk about this, but I'm just letting you guys know: a joke to someone (or some people) might not be such for someone else (or some other people). And this is the point where the line between "friends jokingly insulting each other" and "bullying" is blurred.
You won't see too many in an hour or two, but the notifications quickly add-up over time. Most of it is off-topic discussing / spam, but recently I have been surprised by the amount of on-topic discussion, as mentioned in this quote: