Entity reference formatter should default to the 'Default' view mode

Agreed :)

Do you think we should make 'Default' view mode available also in custom blocks, views entity area and row plugins (in follow-ups)?

+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceEntityFormatter.php
@@ -67,6 +67,9 @@ public function settingsSummary() {
+    if ($view_mode == 'default') {
+      $view_mode = t('Default');
+    }
     $summary[] = t('Rendered as @mode', array('@mode' => isset($view_modes[$view_mode]['label']) ? $view_modes[$view_mode]['label'] : $view_mode));

I'm not sure if this would be more readable as:

    if ($view_mode == 'default') {
      $view_mode = t('Default');
    }
    elseif (isset($view_modes[$view_mode]['label'])) {
      $view_mode = $view_modes[$view_mode]['label'];
    }
    $summary[] = t('Rendered as @mode', array('@mode' => $view_mode));

Committed 6023052 and pushed to 8.x. Thanks!

Filed #2057199: Unable to select the 'Default' view mode for custom block, #2057203: Unable to select the 'Default' view mode in views entity area handler and #2057207: Unable to select the 'Default' view mode in views entity row plugin.

Hmm. Found this saying:

An additional 'default' view mode is available for all entity types. This view mode is not intended for actual entity display, but holds default display settings.

Also: the default value for view mode is "full" here, but not all entity types have it.

So instead of providing the 'Default', what about providing the 'Full'? Or should we just change the docs by removing "is not intended for actual entity display, but" and maybe change the default value from "full" to "default"?