diff --git a/docs/topics/api/activity.rst b/docs/topics/api/activity.rst
index 9697194f32..2c4c5d92ec 100644
--- a/docs/topics/api/activity.rst
+++ b/docs/topics/api/activity.rst
@@ -40,9 +40,9 @@ Review Notes Detail
 This endpoint allows you to fetch a single review note for a specific version of an add-on.
 
     .. note::
-        To allow reviewers to stay anonymous if they wish, the ``user`` object ``name`` can point to
-        their "reviewer" name depending on the action. In addition all other fields in that object,
-        despite being present for backwards-compatibility, are set to ``null``.
+        To allow reviewers to stay anonymous if they wish, the ``user`` object
+        only contains the name of the reviewer or author. That name may, for
+        some actions, be an alias and not the usual name of the user.
 
 .. http:get:: /api/v4/addons/addon/(int:addon_id|string:addon_slug|string:addon_guid)/versions/(int:id)/reviewnotes/(int:id)/
 
@@ -51,10 +51,7 @@ This endpoint allows you to fetch a single review note for a specific version of
     :>json int id: The id for a review note.
     :>json string action: The :ref:`type of review note<review-note-action>`.
     :>json string action_label: The text label of the action.
-    :>json int|null user.id: The id of the reviewer or author who left the review note.
     :>json string user.name: The name of the reviewer or author.
-    :>json string|null user.url: The link to the profile page for of the reviewer or author.
-    :>json string|null user.username: The username of the reviewer or author.
     :>json string comments: The text content of the review note.
     :>json string date: The date the review note was created.
 
diff --git a/src/olympia/activity/serializers.py b/src/olympia/activity/serializers.py
index 7f88288595..e2c9f4e26d 100644
--- a/src/olympia/activity/serializers.py
+++ b/src/olympia/activity/serializers.py
@@ -3,6 +3,7 @@ from django.utils.translation import ugettext
 from rest_framework import serializers
 
 from olympia.activity.models import ActivityLog
+from olympia.api.utils import is_gate_active
 
 
 class ActivityLogSerializer(serializers.ModelSerializer):
@@ -42,10 +43,16 @@ class ActivityLogSerializer(serializers.ModelSerializer):
         avoid revealing actual name of reviewers for their review actions if
         they have set an alias.
 
-        id, username and url are present for backwards-compatibility only."""
-        return {
-            'id': None,
-            'username': None,
-            'url': None,
+        id, username and url are present for backwards-compatibility in v3 API
+        only."""
+        data = {
             'name': obj.author_name,
         }
+        request = self.context.get('request')
+        if request and is_gate_active(request, 'activity-user-shim'):
+            data.update({
+                'id': None,
+                'username': None,
+                'url': None
+            })
+        return data
diff --git a/src/olympia/activity/tests/test_serializers.py b/src/olympia/activity/tests/test_serializers.py
index b2df27da52..153b415706 100644
--- a/src/olympia/activity/tests/test_serializers.py
+++ b/src/olympia/activity/tests/test_serializers.py
@@ -44,30 +44,39 @@ class TestReviewNotesSerializerOutput(TestCase, LogMixin):
         assert result['action_label'] == 'Rejected'
         assert result['comments'] == u'Oh nøes!'
         # To allow reviewers to stay anonymous the user object only contains
-        # the "activity name", which uses the reviewer name alias if present.
+        # the author name, which can use the reviewer name alias if present
+        # depending on the action.
         assert result['user'] == {
-            'id': None,
-            'name': 'fôo',
-            'url': None,
-            'username': None,
+            'name': self.user.reviewer_name,
         }
 
-    def test_url_for_yourself(self):
-        self.request.user = self.user
+    def test_basic_v3(self):
+        self.request.version = 'v3'
         result = self.serialize()
-        assert result['user']['url'] is None
 
-    def test_url_for_developers(self):
-        addon_factory(users=[self.user])
-        result = self.serialize()
-        assert result['user']['url'] is None
+        assert result['id'] == self.entry.pk
+        assert result['date'] == self.now.isoformat() + 'Z'
+        assert result['action'] == 'rejected'
+        assert result['action_label'] == 'Rejected'
+        assert result['comments'] == u'Oh nøes!'
+        # For backwards-compatibility in API v3 the id, url and username are
+        # present but empty - we still don't want to reveal the actual reviewer
+        # info.
+        assert result['user'] == {
+            'id': None,
+            'url': None,
+            'username': None,
+            'name': self.user.reviewer_name,
+        }
 
-    def test_url_for_admins(self):
-        admin = user_factory()
-        self.grant_permission(admin, 'Users:Edit')
-        self.request.user = admin
+    def test_basic_somehow_not_a_reviewer_action(self):
+        """Like test_basic(), but somehow the action is not a reviewer action
+        and therefore shouldn't use the reviewer_name."""
+        self.entry.update(action=amo.LOG.ADD_RATING.id)
         result = self.serialize()
-        assert result['user']['url'] is None
+        assert result['user'] == {
+            'name': self.user.name,
+        }
 
     def test_should_highlight(self):
         result = self.serialize(context={'to_highlight': [self.entry]})
diff --git a/src/olympia/lib/settings_base.py b/src/olympia/lib/settings_base.py
index f23ac48af5..b4045cbeb9 100644
--- a/src/olympia/lib/settings_base.py
+++ b/src/olympia/lib/settings_base.py
@@ -1654,6 +1654,7 @@ DRF_API_GATES = {
         'del-accounts-fxa-edit-email-url',
         'del-version-license-is-custom',
         'del-ratings-flags',
+        'activity-user-shim',
     ),
     'v4': (
         'l10n_flat_input_output',