Google+ Mute Keyboard Shortcut Userscript

plusmute.user.js

// ==UserScript==
// @name          Google+ Mute Keyboard Shortcut
// @namespace     http://antimatter15.com/
// @description   Mute conversations in your stream by hitting "m"
// @include       https://plus.google.com/*
// @include       http://plus.google.com/*
// @version       1.2
// ==/UserScript==

document.addEventListener('keydown', function(e){
  function mouse(name){
    var evt = document.createEvent("MouseEvents");
    evt.initMouseEvent(name ? ('mouse'+name) : 'click', true, true, window, 0, 0, 0, 1, 1, false, false, false, false, 0, null);
    return evt;
  }
  if(e.keyCode == 77 && !(document.activeElement.isContentEditable || /input|textarea/i.test(document.activeElement.tagName))){
    var selected = [].slice.call(document.querySelectorAll('#contentPane div[id^=update]'),0).filter(function(i){
      return getComputedStyle(i).getPropertyValue('border-left-color') == 'rgb(77, 144, 240)'
    })[0];
    
    if(!selected) return;
    var undo_mute = selected.querySelector("span[title=Undo]");
    if(!undo_mute || window.getComputedStyle(undo_mute.parentNode.parentNode.parentNode).display == 'none'){
      selected.querySelector('span[title="Options menu"]').dispatchEvent(mouse('down'));
      var mute = [].slice.call(selected.querySelectorAll('div[role=menuitem]'),0).filter(function(e){
        return ~e.innerHTML.indexOf('Mute')
      })[0];
      mute.dispatchEvent(mouse('down'));
      mute.dispatchEvent(mouse('up'));
    }else{
      undo_mute.dispatchEvent(mouse());
    }
  }
}, true)

forked, and fixed: https://gist.github.com/1609306