None of that round corner rubbish

edgy_twitter.js

// ==UserScript==
// @name         Edgy Twitter
// @namespace    https://twitter.com/l_h_hacker
// @version      19.84
// @description  None of that round corner rubbish
// @author       sebastian (@l_h_hacker)
// @include      https://twitter.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    var body = document.getElementsByTagName('body')[0];
    body.classList.remove('edge-design');

    var bodyObserver = new MutationObserver(function(mutations) {

        if(body.classList.contains('edge-design')) {
            body.classList.remove('edge-design');
        }
    });

    bodyObserver.observe(body, {attributes: true, attributeFilter: ['class']});

})();