Updated: Comment #23
When a theme suggestion is called directly, like
theme('comment__node__article', …), the Twig debug output does not show the base template - in this case comment.html.twig, or the derived template comment--node.html.twig.
Add code to twig.engine to handle this scenario and display all possible template suggestions in the correct order
User interface changes
Twig debug output will display the base template and derived template suggestions when theme suggestions are called directly. Suggestions added via preprocess (theme_hook_suggestions) will display in the correct order.