While you can’t automate adding the Read More… into your blogs, you can automate the Commento comments with some custom JS. This is what the code will look like:
// src: https://cdn.commento.io/js/commento.js
var topP = document.createElement("p");
topP.innerHTML = '<div id="commento"></div>';
var cont = document.getElementById("wrapper");
cont = document.getElementById("post-body");
cont.appendChild(topP);
Then all you have to do is add <!--more--> at the end of your posts and that should do the trick. Let me know if that works for you!