To reproduce:
Grab latest head, and install standard profile.
Go straight to the module page and disable and then uninstall comment
Run cron to trigger field_purge_batch() (twice to be sure)
Go to dblog
Observe some exceptions that look like:
Drupal\field\FieldException: Attempt to create an instance of unknown field 1ee73fab-78da-499d-b306-6c78a15879b6 in Drupal\field\Plugin\Core\Entity\FieldInstance->__construct() (line 223 of /var/www/d8/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstance.php).
1ee73fab-78da-499d-b306-6c78a15879b6 is the Uuid of the instance
a debug bactrace here:
https://privatepaste.com/c1adf5434c