The latest FB oddity, and social networks are odd enough to begin with, is that you can request your friends to click on your profile picture and make any comments you leave on their page invisible to the rest of the world.
I had to think on this one...First, if you're going to leave comments that are included in public discussions and posts on someone else's page, why not let everyone see them? Second, why make someone else responsible for the privacy of your comments that you are leaving on their public page? And what if, just what if, your friends don't want to click on your public profile picture and follow through with this request? What are you going to do then, huh?...refuse to post on their wall? unfriend them?
And why would anyone make such a request in the first place? Quite frankly, it makes you look sneaky.
You have to suspect that this request comes from someone who may want to leave snarky bitchy comments, and they want to wallow in their witty sarcasms with the safe and secure knowledge that their target is unaware of their actions.
Look at it this way-- if you really have something private to say to someone, you can send them a private message-- that's what this is for...hello? Otherwise, stay the fuck off their public page.