Confirmation message on comment submission

Question

When a comment is submitted, no confirmation message is shown and I would like to achieve this. I want to show the following message.

Your comment has been added for review and approval.

I tried this code.

function mymod_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  else if ($form_id == 'comment_comment_form') {
    $form['actions']['submit']['#value'] = "your comment has been added for review and approval"
  }
}

This only edits the submission button text. Is there a way to add a submission confirmation message?

Answer 1

Drupal already shows a similar message, to the users who has the post comments permission but not the skip comment approval permission.
There is no need to use custom code for that: Don't give the skip comment approval permission to the users whose comments must be approved.

If the purpose is changing the message shown by Drupal in that case (Your comment has been queued for review by site administrators and will be published after approval.), it's enough to change the message Drupal uses, for example adding the following line to the settings.php file.

$settings['locale_custom_strings_en'][''] = [
  'Your comment has been queued for review by site administrators and will be published after approval.' => 'Your comment has been added for review and approval',
];

Answer 2

You would need to add a custom submit handler, and set your message there.

function ahrq_form_alter(&$form, FormStateInterface $form_state, $form_id) {
    else if($form_id == 'comment_comment_form') {
       $form['actions']['submit']['#submit'][] = 'ahrq_comment_form_submit';
    }
}

function ahrq_comment_form_submit(&$form, FormStateInterface $form_state) {
  \Drupal::messenger()->addStatus->($this->t('Your comment has been added for review and approval'));
}