the method of your form is still to post to another page:
<form action="../form_response.html" method="post" id="comments_form">
Rule #1 when working with forms:
All form Processing must occur on the forms action page. for captcha to work, the server validation needs to be added to the forms action page.
normally the work flow with server validation for form toolkit is to set the form to post to itself, use server validation to validate the captcha, and use Universal Email so send the email. in universal Email you can set the redirect to go to another page.