How do I switch off the activity feed or delete comments?
Go to Setup > General. Scroll to the bottom of the page and click to Show Advanced Options.
Uncheck the Activity Feed box and click to SAVE.
The activity feed for an individual item can be disabled in the Advanced Options in the item set up. Edit item then expand Advanced Options and uncheck the activity feed box.
Delete a comment
To delete Individual comments go to the Communication Section in the left menu and click the Activity feed tab.