You don't have to "police" Discord to respond to something to players on your game. Much like @mietze said, if it's happening on Discord? It's happening all over your game, or they just took it to Discord to feel 'protected' from staff or whatever.
If anyone came to me and said their crazy ex who beat them was on the game and they needed help, I wouldn't think twice to nuke the toon. Just like if I was a manager at McDonald's and someone came up to me and asked me for help because their crazy ex who beat them is here, I would pick up the phone and call the police and put the woman somewhere where she can feel safe. It's like, the very basic of what a decent human being would do even if it's not expressly in your job title or whatever.