Sigh.

fix_reddit.user.js

// ==UserScript==
// @name         Actually fixed reddit UI
// @namespace    http://yanrishatum.ru/
// @version      0.2
// @description  For fucks sake, it's PC, we don't need that much negative space and nags.
// @author       Yanrishatum
// @match        *://reddit.com/*
// @match        *://*.reddit.com/*
// @grant        none
// ==/UserScript==

(function() {
  'use strict';
  var style = document.createElement("style");
  document.head.appendChild(style);
  style = style.sheet;
  
  var base = document.querySelector("#SHORTCUT_FOCUSABLE_DIV>div>div>div:nth-child(3)>div>div>div:nth-child(2)>div:nth-child(3)");
  if (!base) base = document.querySelector("#SHORTCUT_FOCUSABLE_DIV>div>div>div:nth-child(3)>div>div>div>div:nth-child(2)>div:nth-child(2)");
  var sidebar = base.children[1].firstElementChild;
  
  // Disable nagging header
  style.insertRule("#header { position: absolute; }");
  // Right bar nag adjust
  style.insertRule("." + sidebar.children[sidebar.children.length-1].classList[1] + ">div:nth-child(1) { top: 0; }");
  
  // NEGATIVE SPAAAAAAAAAAAAAAAACEEEEEEE
  style.insertRule("." + base.classList[1] + " { padding: 0; margin: 0; max-width: initial; }");
  style.insertRule("." + base.children[1].classList[1] + " { margin-left: 0; }");
  style.insertRule(
    "." + sidebar.children[0].classList[1] + ", " +
    "." + sidebar.children[0].classList[1] + ">div, " +
    "." + sidebar.children[1].classList[1] + ", " +
    "." + sidebar.children[1].classList[1] + ">div" +
    " { border-radius: 0; border: none; box-shadow: none; }");
  style.insertRule("." + sidebar.children[1].classList[1] + " { margin-top: 0; }");
  
  // Dynamic shit
  try
  {
    for (var css of document.styleSheets)
    {
      for (var rule of css.cssRules)
      {
        if (rule instanceof CSSMediaRule)
        {
          // Cards
          if (rule.cssText.indexOf("648px") != -1)
          {
            style.insertRule(rule.cssRules[0].selectorText + " { width: 100%; }");
            style.insertRule(rule.cssRules[0].selectorText + " div.scrollerItem { margin-bottom: 0; border-radius: 0; border-width: 1px 0px 0px 0px; }");
          }
          else if (rule.cssText.indexOf("calc(((100% + 0px) - 984px) / 2)") != -1)
          {
            style.insertRule(rule.cssRules[0].selectorText + " { left: 24px; }");
          }
          else if (rule.cssText.indexOf("864px") != -1)
          {
            style.insertRule(rule.cssRules[0].selectorText + " { width: 100%; }");
            style.insertRule(rule.cssRules[0].selectorText + ">div { max-width: initial; border-radius: 0; }");
          }
        }
      }
    }
  }
  catch (e)
  {
    // Failed to read bla bla bla
  }
  // Ads
  // If only there was :has...
  style.insertRule("div[data-slot] { display: none; }");
})();