Update to Drupal 8.0.0-beta15. For more information, see: https://www.drupal.org/node/2563023

core/modules/comment/config/optional/views.view.comments_recent.yml

@@ -119,7 +119,7 @@ display:
           table: comment_field_data
           field: changed
           relationship: none
-          plugin_id: date
+          plugin_id: field
           group_type: group
           admin_label: ''
           label: ''
@@ -163,9 +163,11 @@ display:
           hide_empty: false
           empty_zero: false
           hide_alter_empty: true
-          date_format: 'time ago'
-          custom_date_format: ''
-          timezone: ''
+          type: timestamp_ago
+          settings:
+            future_format: '@interval hence'
+            past_format: '@interval ago'
+            granularity: 2
           entity_type: comment
           entity_field: changed
       filters:

core/modules/comment/config/schema/comment.source.schema.yml

@@ -0,0 +1,35 @@
+migrate.source.d6_comment:
+  type: migrate_source_sql
+  label: 'Drupal 6 comment'
+  mapping:
+    constants:
+      type: mapping
+      label: 'Constants'
+      mapping:
+        entity_type:
+          type: string
+          label: 'Entity type'
+
+migrate.source.d6_comment_variable_per_comment_type:
+  type: migrate_source_sql
+  label: 'Drupal 6 comment variable'
+  mapping:
+    constants:
+      type: migrate_entity_constant
+      label: 'Constants'
+
+migrate.source.d6_comment_entity_form_display_subject:
+  type: migrate_source_sql
+  label: 'Drupal 6 comment subject entity form display'
+  mapping:
+    constants:
+      type: migrate_entity_constant
+      label: 'Constants'
+
+migrate.source.d6_comment_variable:
+  type: migrate_source_sql
+  label: 'Drupal 6 comment variable'
+  mapping:
+    constants:
+      type: migrate_entity_constant
+      label: 'Constants'