Yes, indeed, if you're looking to scale up to handle high concurrent user loads, scaling out horizontally is your best bet. We've got a client right now serving 700+ connections at the moment, and they're on four separate NodeBB instances. It's probably too much for what they need, but it's always nice to have more capacity than needed in case of spikes, etc.
@Nivix You don't grant the users actual power. Someone from YouTube said the same thing. (Can't find it where he said it though, probably in one of his livestreams) But the way to do this is to setup some clear guidelines on how you want your users to behave, Let the users engage the user in question without harassing him. Thats basically the whole trick. Adjusting is easier if the whole group communicates in the same way.