Use a new container for new captchas.

src/Posting/QR.captcha.coffee

@@ -10,20 +10,15 @@ QR.captcha =
 
     section = $.el 'div', className: 'captcha-section'
     $.extend section, <%= html(
-      '<div class="captcha-container"></div>' +
       '<div class="captcha-counter"><a href="javascript:;"></a></div>'
     ) %>
     container = $ '.captcha-container',   section
     counter   = $ '.captcha-counter > a', section
-    @nodes = {container, counter}
+    @nodes = {section, container, counter}
     @count()
     $.addClass QR.nodes.el, 'has-captcha'
     $.after QR.nodes.com.parentNode, section
 
-    new MutationObserver(@afterSetup.bind @).observe container,
-      childList: true
-      subtree: true
-
     $.on counter, 'click', @toggle.bind @
     $.on window, 'captcha:success', @save.bind @
 
@@ -32,13 +27,13 @@ QR.captcha =
 
   needed: ->
     captchaCount = @captchas.length
-    captchaCount++ if @nodes.container.dataset.widgetID and !@timeouts.destroy
+    captchaCount++ if @nodes.container and !@timeouts.destroy
     postsCount = QR.posts.length
     postsCount = 0 if postsCount is 1 and !Conf['Auto-load captcha'] and !QR.posts[0].com and !QR.posts[0].file
     captchaCount < postsCount
 
   toggle: ->
-    if @nodes.container.dataset.widgetID and !@timeouts.destroy
+    if @nodes.container and !@timeouts.destroy
       @destroy()
     else
       @shouldFocus = true
@@ -51,7 +46,15 @@ QR.captcha =
       clearTimeout @timeouts.destroy
       delete @timeouts.destroy
       return @reload()
-    return if @nodes.container.dataset.widgetID
+
+    return if @nodes.container
+
+    @nodes.container = $.el 'div', className: 'captcha-container'
+    $.prepend @nodes.section, @nodes.container
+    new MutationObserver(@afterSetup.bind @).observe @nodes.container,
+      childList: true
+      subtree: true
+
     $.globalEval '''
       (function() {
         var container = document.querySelector("#qr .captcha-container");
@@ -80,9 +83,8 @@ QR.captcha =
     return unless @isEnabled
     delete @timeouts.destroy
     $.rmClass QR.nodes.el, 'captcha-open'
-    $.rmAll @nodes.container
-    # XXX https://github.com/greasemonkey/greasemonkey/issues/1571
-    @nodes.container.removeAttribute 'data-widget-i-d'
+    $.rm @nodes.container
+    delete @nodes.container
 
   sync: (captchas) ->
     @captchas = captchas