Contributors can manage comments for each post under the Manage Content tab in the portal.
For every piece of content, you will see a Comments icon. Once you click the Comments icon, you are able to respond individually to comments or even delete them. If you do respond or like a comment, it will show that you (the author) commented or liked it.
You also have the ability to control commenting on each post. A toggle at the top, allows you to restrict comments to just your followers or turn off commenting for everyone.