Anytime there is a person's username somewhere, it's a link; you can either click on it or just hover your mouse over it. If you hover your mouse over it a small window will appear that will have a few options. One of those options is "Start Conversation" which is the same as sending a private message in other forum software. So, start a conversation and that should trigger an email alert to the person receiving the message.
If you click on the username link then it will take you to the person's profile page and there are more options there including another "Start Conversation" link.
Profile posts are not private, which you guys have all figured out already.