I believe since you have JS you can do anything. For example a nodejs server, using websockets. Thing is : how would you do a multiplayer visual novel ? I think it's more a matter of design, on how you'll be using Twine for this, because if you do a multiplayer game in a Twine page but composed of 95% JS, does it still worth using Twine ? Besides that, I think there are good ideas in there (I did a multiplayer visual novel long time ago and it was fun)