add anonymous_email_enabled settings to really let integrator activate it. add the migration script which add the option to the registry and do not change the behavior: the email will not be displayed by default

plone/app/discussion/browser/comments.py

@@ -105,13 +105,12 @@ class CommentForm(extensible.ExtensibleForm, form.Form):
             self.widgets['author_name'].mode = interfaces.HIDDEN_MODE
             self.widgets['author_email'].mode = interfaces.HIDDEN_MODE
 
-        # Todo: Since we are not using the author_email field in the
-        # current state, we hide it by default. But we keep the field for
-        # integrators or later use.
-        self.widgets['author_email'].mode = interfaces.HIDDEN_MODE
-
         registry = queryUtility(IRegistry)
         settings = registry.forInterface(IDiscussionSettings, check=False)
+
+        if mtool.isAnonymousUser() and not settings.anonymous_email_enabled:
+            self.widgets['author_email'].mode = interfaces.HIDDEN_MODE
+
         member = mtool.getAuthenticatedMember()
         member_email = member.getProperty('email')
 

plone/app/discussion/interfaces.py

@@ -322,6 +322,15 @@ class IDiscussionSettings(Interface):
         required=False,
         default=False)
 
+    anonymous_email_enabled = schema.Bool(
+        title=_(u"label_anonymous_email_enabled",
+                default=u"Enable anonymous email field"),
+        description=_(u"help_anonymous_email_enabled",
+                      default=u"If selected, anonymous user will have to "
+                      "give their email."),
+        required=False,
+        default=False)
+
 
 class IDiscussionLayer(Interface):
     """Request marker installed via browserlayer.xml.

plone/app/discussion/profiles/default/metadata.xml

@@ -1,5 +1,5 @@
 <metadata>
- <version>100</version>
+ <version>110</version>
  <dependencies>
   <dependency>profile-plone.app.registry:default</dependency>
  </dependencies>

plone/app/discussion/upgrades.py

@@ -6,3 +6,10 @@ from plone.app.discussion.interfaces import IDiscussionSettings
 def update_registry(context):
     registry = getUtility(IRegistry)
     registry.registerInterface(IDiscussionSettings)
+
+
+def add_anonymous_email_enabled_settings(context):
+    registry = getUtility(IRegistry)
+    key = 'plone.app.discussion.interfaces.IDiscussionSettings.'
+    key += 'anonymous_email_enabled'
+    registry[key] = False

plone/app/discussion/upgrades.zcml

@@ -11,4 +11,12 @@
       handler=".upgrades.update_registry"
       />
 
+  <genericsetup:upgradeStep
+      source="*"
+      destination="110"
+      title="Update plone.app.discussion setting registry"
+      description=""
+      profile="plone.app.discussion:default"
+      handler=".upgrades.update_registry"
+      />
 </configure>