Show Comment Form on its own Page or Popup
You can accomplish this using an extra node template for the page where the comment form is displayed:

In your theme file create an extra template suggestion for the comment form:

function HOOK_theme_suggestions_node_alter(array &amp;$suggestions, array $variables) {
    $route_name = \Drupal::service('current_route_match')-&gt;getRouteName();

    if($route_name === 'comment.reply') {
        $suggestions[] = 'node__commentform';
    }
}


Create an extra node template node--commentform.html.twig, and remove just about everything. You probably want to leave the node title, but otherwise there's nothing you need there:

&lt;article{{ attributes }}&gt;

  {{ title_prefix }}
  {% if not page %}
    &lt;h2{{ title_attributes }}&gt;
      &lt;a href="{{ url }}" rel="bookmark"&gt;{{ label }}&lt;/a&gt;
    &lt;/h2&gt;
  {% endif %}
  {{ title_suffix }}
&lt;/article&gt;


The comment form is rendered outside this template, so you don't need any of it.