When a user is added to or removed from an item a membership message is posted to the item (for example, The Conversation is now accessible to: John Doe). If you'd prefer not to see those messages, you can hide them.
Open the item.
Click , then select Hide Membership Messages or Show Membership Messages.
Note: You can set the default view of membership messages for all walls and Conversations through your preferences. For more information, see How do I change my preferences?