Adding a new field to already posted comments

I want to add a checkbox (verify) to each comment so that the author of the post can verify each comment. The checkbox needs to be read-only to anyone but the author of the post. I’ve found different ways on adding new form fields to the comment form, but I only want the field on already posted comments. Can someone point me in the right direction? I have a strong programming background, but WordPress is fairly new to me.