With v10.3 the support for extra comment fields (in addition to author, url, email & comment) has been much improved.
Adding two extra fields (e.g. another text input field + a check box) only takes a few steps now, here is how it's done:
[#1] Form Configuration:
Extend your form by adding those two more fields ( note the required [id:customX] ):


Other required settings:


[#2] The above will make the (default WP comment) form look like:


Only the extra fields will be stored in the cforms tracking tables:


[#3] Now adjust your WP's comment.php template:
Add inside the LOOP:
<?php $xtra = cf_extra_comment_data(get_comment_ID()); ?>
The data array $xtra can now be referenced, e.g. right after the comment_author_link() in this example:
— <?php echo ' Agreed: '.($xtra['My custom checkbox']<>''?'Yes':'No'); ?>
[#4] Outputs:
