Userscript to follow topics you post on.

topicfollower.user.js

// ==UserScript==
// @name         Topic Follower
// @namespace    http://ateesdalejr.tk/
// @version      1.0
// @description  Follows any topic you post on.
// @author       TheUltimatum
// @match        https://scratch.mit.edu/discuss/topic/*
// @updateURL    https://rawgit.com/ateesdalejr/2ea978e39d48f0315a9d972bde05ceae/raw/cef03f1e53056013005b44aa9b9f099897a25a4c/topicfollower.user.js
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    document.getElementById("post").onsubmit = function() {
        $.ajax({
            method: "POST",
            url: "/discuss/subscription/topic/" + location.pathname.split("/")[3] + "/add/",
            data: {
                csrfmiddlewaretoken: getCookie("scratchcsrftoken")
            }
        });
    };
})();