I have been using this field in a recent project needed to migrate data to it. No migrate handler existed so I created one. Probably the easiest five minutes I have used to program Drupal.
I have submitted it too https://www.drupal.org/node/2541912
But for those looking to migrate to this field use this code
<?php
class MigrateCommentFieldHandler extends MigrateFieldHandler {
public function __construct() {
$this->registerTypes(array('commentfield'));
}
public function prepare($entity, array $field_info, array $instance, array $values) {
// Setup the Field API array for saving.
$arguments = (isset($values['arguments'])) ? $values['arguments']: array();
$language = $this->getFieldLanguage($entity, $field_info, $arguments);
$delta = 0;
foreach ($values as $value) {
$return[$language][$delta]['comment'] = $value['comment'];
$return[$language][$delta]['created'] = $value['created'];
$return[$language][$delta]['uid'] = $value['uid'];
$delta++;
}
return isset($return) ? $return : NULL;
}
}
?>