On mouseover of a review, you have an option to create a reply on the review with comments by clicking on 
icon.
Enter a reply on the review comment as required. You can specifically mention a project member in your review comment by typing '@' and then select name of that particular member wherever required from the suggested dropdown list. Type the initial characters if there is a long list of project members to filter the list accordingly.
Reply notification will only be sent to users who were specifically mentioned in the reply comment.
icon - Click to attach external files from your computer. It populates a layered page allowing you to select and upload files from your local device storage.
icon - Click to view association options which includes 'Associate Files', 'Associate Reviews' and 'Associate Apps'.Associate Files - Click to associate documents to this review comment. Clicking the link, a layered page populates displaying the files you can select to associate with the review comment being created.
Associate Reviews - Click to associate other review comments to this review comment. Clicking the link, a layered page populates displaying the file review comments you can select to associate with the review comment being created.
Associate Apps - Click to associate forms to this review comment. Clicking the link, a layered page populates displaying the forms you can select to associate with the review comment being created.
Associate Markups - Click to associate markups to this review comment. Clicking the link, a layered page populates displaying the markups you can select to associate with the review comment being created.
icon - Click to view toolbar having rich text options (appears as a top bar in comment box) that you can use while creating the review comment.
icon - Click to save the review comment you entered.
Next Article: Mark Review as Private