There are no distinct boundaries between griefing, trolling and flamebaiting. I'd argue the groups with intentionally offensive names are griefers by default. Is intentionally triggering a negative reaction in someone for lulz using an off-topic comment and claiming "it's just a joke, bro" trolling, flamebaiting or griefing? Depends who you ask, but I'm glad none of the overt versions of the three are welcome on HN.