Implements hook_preprocess_HOOK() for node.html.twig.
function bartik_preprocess_node(&$variables) {
// Remove the "Add new comment" link on teasers or when the comment form is
// displayed on the page.
if ($variables['teaser'] || !empty($variables['content']['comments']['comment_form'])) {
unset($variables['content']['links']['comment']['#links']['comment-add']);
}
}