The MainWP Comments Extension allows you to Approve, Disapprove, Mark as spam, Un-spam, Edit and Delete comments in all your child sites from one place. By using bulk actions you will save time for more important tasks or if you prefer you can still moderate your comments one by one.
The Recent Comments Widget
A Great addition to this extension is the Recent Comments widget. You will always be able to track the latest Approved, Pending and Trashed comments in your sites. You can also use the provided links to quickly moderate the latest comments.