I'm not certain what you are referring to. You can post in their shout boxes, if you've allowed that element for them to use. Anything that you post on a profile will be seen by the member. The members themselve's have the control as to who all can see what is posted on their profile, and they do so by adjusting their privacy settings. They can choose who can view their profile in general. If you have some sort of message you'd like to give to "just them", so that no one else sees it, you'd probably want to use the private message system, and just send them a message.
