Cannot see my friends comment history on FB?

[Cry Baby Obama]

Your controls are right next to each thing you share. Use the audience selector to choose who can see what you're sharing. The audience you choose appears along with whatever you are saying. You can also use the tool to change who you are sharing with after you post.

Have something you only want to share with only a few friends? Send a message, create a group, or share with a friend list of your choice.

Your posts that are not on your own profile (timeline)

You will not be able to use the audience selector unless you are posting on your own profile (timeline). If you post to another person's profile (timeline), the person whose profile (timeline) you are posting to controls what audience can view your post.