Seems Facebook users are born in 2009 or after wards. Every email service sends your IP address with the email. The exception is Google.
2) Someone who is not even my friend commented on someone's status, and I got a notification because I made a comment before her. It leaked her IP address to me.
These situations are not comparable to e-mail, and I seriously doubt these people reasonably expected their IP address to be sent to me based on these actions.