CommentTypeForm::form

public CommentTypeForm::form(array $form, FormStateInterface $form_state)

public function form(array $form, FormStateInterface $form_state) {
  $form = parent::form($form, $form_state);

  $comment_type = $this->entity;

  $form['label'] = array(
    '#type' => 'textfield',
    '#title' => t('Label'),
    '#maxlength' => 255,
    '#default_value' => $comment_type->label(),
    '#required' => TRUE,
  );
  $form['id'] = array(
    '#type' => 'machine_name',
    '#default_value' => $comment_type->id(),
    '#machine_name' => array(
      'exists' => '\Drupal\comment\Entity\CommentType::load',
    ),
    '#maxlength' => EntityTypeInterface::BUNDLE_MAX_LENGTH,
    '#disabled' => !$comment_type->isNew(),
  );

  $form['description'] = array(
    '#type' => 'textarea',
    '#default_value' => $comment_type->getDescription(),
    '#description' => t('Describe this comment type. The text will be displayed on the <em>Comment types</em> administration overview page.'),
    '#title' => t('Description'),
  );

  if ($comment_type->isNew()) {
    $options = array();
    foreach ($this->entityManager->getDefinitions() as $entity_type) {
      // Only expose entities that have field UI enabled, only those can
      // get comment fields added in the UI.
      if ($entity_type->get('field_ui_base_route')) {
        $options[$entity_type->id()] = $entity_type->getLabel();
      }
    }
    $form['target_entity_type_id'] = array(
      '#type' => 'select',
      '#default_value' => $comment_type->getTargetEntityTypeId(),
      '#title' => t('Target entity type'),
      '#options' => $options,
      '#description' => t('The target entity type can not be changed after the comment type has been created.')
    );
  }
  else {
    $form['target_entity_type_id_display'] = array(
      '#type' => 'item',
      '#markup' => $this->entityManager->getDefinition($comment_type->getTargetEntityTypeId())->getLabel(),
      '#title' => t('Target entity type'),
    );
  }

  if ($this->moduleHandler->moduleExists('content_translation')) {
    $form['language'] = array(
      '#type' => 'details',
      '#title' => t('Language settings'),
      '#group' => 'additional_settings',
    );

    $language_configuration = ContentLanguageSettings::loadByEntityTypeBundle('comment', $comment_type->id());
    $form['language']['language_configuration'] = array(
      '#type' => 'language_configuration',
      '#entity_information' => array(
        'entity_type' => 'comment',
        'bundle' => $comment_type->id(),
      ),
      '#default_value' => $language_configuration,
    );

    $form['#submit'][] = 'language_configuration_element_submit';
  }

  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Save'),
  );

  return $form;
}