diff --git a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
index 04a66a9..5270931 100644
--- a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -696,6 +696,8 @@ public function buildOverviewForm(array $form, FormStateInterface $form_state) {
 
     if ($date_performed = $this->state->get('migrate_drupal_ui.performed')) {
       // @todo Add back support for rollbacks and incremental migrations.
+      //   https://www.drupal.org/node/2687843
+      //   https://www.drupal.org/node/2687849
       $form['upgrade_option_item'] = [
         '#type' => 'item',
         '#prefix' => $this->t('An upgrade has already been performed on this site. To perform a new migration, create a clean and empty new install of Drupal 8. Rollbacks and incremental migrations are not yet supported through the user inteface. For more information, see the <a href=":url">upgrading handbook</a>.', [':url' => 'https://www.drupal.org/upgrade/migrate']),
diff --git a/core/modules/migrate_drupal_ui/src/MigrateUpgradeRunBatch.php b/core/modules/migrate_drupal_ui/src/MigrateUpgradeRunBatch.php
index a614d93..967cd62 100644
--- a/core/modules/migrate_drupal_ui/src/MigrateUpgradeRunBatch.php
+++ b/core/modules/migrate_drupal_ui/src/MigrateUpgradeRunBatch.php
@@ -69,6 +69,9 @@ class MigrateUpgradeRunBatch {
    *   An array of additional configuration from the form.
    * @param array $context
    *   The batch context.
+   *
+   * @todo Remove the $operation parameter and conditionals for it below, and
+   *   refactor this method. https://www.drupal.org/node/2687851
    */
   public static function run($initial_ids, $operation, $config, &$context) {
     if (!static::$listenersAdded) {