JLinked will send the new user emails to any user that is marked as "Receive System Emails" in their user account. That is a setting only available to be set in the admin area, not from the front-end.
You'll need to check if, and why, your users have that setting enabled. That setting is used by many extensions for 'system notifications' of different events, like problems detected, and by Joomla itself for notifications of new users. We're simply using that system built-in to Joomla.
Hope that helps explain. If you find that users don't have that setting enabled, let us know, and we can look into it further as a bug!