I'm on an online chat system for a game and one player said "Mr X needs to be stabbed in the throat" (actual name changed). The statement was accompanied by an image designed to give maximum offense. It was clear they meant in real life, not in the game. The player who said this has a history of aggressive and violent online speech that goes beyond what happens in the game.
The player who said this, "Mr X", and I are all in Australia. Is this illegal in Australia?