Derp, simpler code.

4chan_x.user.js

@@ -2002,16 +2002,8 @@
       scrollBG: function() {
         return updater.scrollBG = this.checked ? function() {
           return true;
-        } : d.visibilityState ? function() {
-          return !d.hidden;
-        } : d.oVisibilityState ? function() {
-          return !d.oHidden;
-        } : d.mozVisibilityState ? function() {
-          return !d.mozHidden;
-        } : d.webkitVisibilityState ? function() {
-          return !d.webkitHidden;
         } : function() {
-          return true;
+          return !(d.hidden || d.oHidden || d.mozHidden || d.webkitHidden);
         };
       },
       update: function() {

script.coffee

@@ -1612,16 +1612,7 @@ updater =
         if @checked
           -> true
         else
-          if d.visibilityState
-            -> !d.hidden
-          else if d.oVisibilityState
-            -> !d.oHidden
-          else if d.mozVisibilityState
-            -> !d.mozHidden
-          else if d.webkitVisibilityState
-            -> !d.webkitHidden
-          else
-            -> true
+          -> !(d.hidden or d.oHidden or d.mozHidden or d.webkitHidden)
     update: ->
       if @status is 404
         updater.timer.textContent = ''