Step 1 Press Insert + F6 to get a list of header tags on the page.

Step 2 Select the h2 tag with a name n Comments :2. n refers to the number of comments on the page. For example, if there are 4 comments on the page, select the 4 Comments :2 header. Then press Enter to get the focus on the Comments header. If you don't find a header matching to the above pattern, there will be no comments.

Step 3 Press Tab to navigate among the authors of the comments. 

Step 4 Once you landed on the comment that you need to reply, press Down Arrow until JAWS says Link Reply.

Step 5 Then press Enter to access the prompt that allows to write a reply comment to another comment.

Step 6 Next press Alt + e and then press e to get the focus to start writing the comment.

Step 7 Type your comment.

Step 8 To save, press Insert + F5 to get a list of form fields. Search for Save Button and press Enter to select it and press Enter again to save the comment. Alternatively you can press Control + S to save the comment.

Step 9 To cancel, press Insert + F5 to get a list of form fields. Search for Cancel Button and press Enter to select it and press Enter again to cancel and exit the comment prompt.