I have gotten the template comments to show up previously. Not sure what the problem is this time. My development.services.yml file looks like...
parameters: http.response.debug_cacheability_headers: true services: cache.backend.null: class: Drupal\Core\Cache\NullBackendFactory parameters: twig.config: debug: true auto_reload: true cache: false
I cleared all caches. I have tried "view source" in FF and Chrome.
If I dump $settings['container_yamls'] in settings.local.php, I see that Drupal has the right path for development.services.yml. And there are no problems in the status report page.