Wordpress - Commenting in user profile page?

Hi @Towfiq:

Comments are related in the database to Posts. You'll have to do a lot of work to get Comments to relate to Users.

Have you considered creating a Custom Post Type for Users and then use either a user_meta field to store the post_id, or a postmeta field to store the user_id, or both? If you did that then you would get the comments with no effort at all.

UPDATE

What follows is code developed after our discussion in the comments.

I've been meaning to write something like this for a long time but your question finding got me to make it a priority. I've created a 'towfiq-person' custom post type for you and I've set it up to automatically add a Person post whenever a User is added and it uses the email address as the associating key in a post custom field called '_email'.

It also associates a User with an appropriate email address to the Person post if a User is added or updated with the same email as an existing Person (this may or may not be a good idea.) And it cross-references User with Person and Person with User using postmeta and usermeta fields '_user_id' and '_person_id', respectively.

These are of course business rules I chose to implement but they may turn out not to be appropriate for your use-case in which case you may need to modify them. You also may find ways that WordPress allows these two to get out of sync but it's hard to know that without exhaustive testing. If you find issues you can always look to update the logic to resolve them.

You can copy the following code to your theme's functions.php file:

class Towfiq_Person {
  static function on_load() {
    add_action('init',array(__CLASS__,'init'));
    add_action('wp_insert_post',array(__CLASS__,'wp_insert_post'),10,2);
    add_action('profile_update',array(__CLASS__,'profile_update'),10,2);
    add_action('user_register',array(__CLASS__,'profile_update'));
    add_filter('author_link',array(__CLASS__,'author_link'),10,2);
    add_filter('get_the_author_url',array(__CLASS__,'author_link'),10,2);
  }
  static function init() {
    register_post_type('towfiq-person',
      array(
        'labels'          => array('name'=>'People','singular_name'=>'Person'),
        'public'          => true,
        'show_ui'         => true,
        'rewrite'         => array('slug' => 'people'),
        'hierarchical'    => false,
        //'supports'        => array('title','editor','custom-fields'),
      )
    );
  }
  static function get_email_key() {
    return apply_filters( 'person_email_key', '_email' );
  }
  static function profile_update($user_id,$old_user_data=false) {
    global $wpdb;
    $is_new_person = false;
    $user = get_userdata($user_id);
    $user_email = ($old_user_data ? $old_user_data->user_email : $user->user_email);
    $email_key = self::get_email_key();
    $person_id = $wpdb->get_var($wpdb->prepare("SELECT post_id FROM {$wpdb->postmeta} WHERE meta_key='%s' AND meta_value='%s'",$email_key,$user_email));
    if (!is_numeric($person_id)) {
      $person_id = $is_new_person = wp_insert_post(array(
        'post_type' => 'towfiq-person',
        'post_status' => 'publish',   // Maybe this should be pending or draft?
        'post_title' => $user->display_name,
      ));
    }
    update_user_meta($user_id,'_person_id',$person_id);
    update_post_meta($person_id,'_user_id',$user_id);
    if ($is_new_person || ($old_user_data && $user->user_email!=$old_user_data->user_email)) {
      update_post_meta($person_id,$email_key,$user->user_email);
    }
  }
  static function wp_insert_post($person_id,$person) {
    if ($person->post_type=='towfiq-person') {
      $email = get_post_meta($person_id,self::get_email_key(),true);
      if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $user = get_user_by('email',$email);
        if ($user) { // Associate the user IF there is an user with the same email address
          update_user_meta($user->ID,'_person_id',$person_id);
          update_post_meta($person_id,'_user_id',$user->ID);
        } else {
          delete_post_meta($person_id,'_user_id');
        }
      }
    }
  }
  static function get_user_id($person_id) {
    return get_user_meta($user_id,'_user_id',true);
  }
  static function get_user($person_id) {
    $user_id = self::get_user_id($person_id);
    return get_userdata($user_id);
  }
  static function get_person_id($user_id) {
    return get_user_meta($user_id,'_person_id',true);
  }
  static function get_person($user_id) {
    $person_id = self::get_person_id($user_id);
    return get_post($person_id);
  }
  static function author_link($permalink, $user_id) {
    $author_id = get_user_meta($user_id,'_person_id',true);
    if ($author_id) // If an associate is found, use it
      $permalink = get_post_permalink($author_id);
    return $permalink;
  }
}
Towfiq_Person::on_load();

If you need any clarifications to what I did and why, just ask in the comments.