The problems is with the comment form structure. It's changed from D6 to D7.

The comment body in D6 was stored in $form['comment_filter'] but in D7 it's $form['comment_body']

If you change this:

//Comment
$form['your_comment']['comment_filter']['comment'] = $form['comment_filter']
['comment'];
unset($form['comment_filter']['comment']);


to this:

//Comment
$form['your_comment']['comment_body']['comment'] = $form['comment_body']
['comment'];
unset($form['comment_body']['comment']);


that might get rid of your errors, but I haven't tested it.

There may be other parts of the comment form that have changed so I would recommend looking at the Drupal API

Plus you can install the Devel module and chart out the new form structures for D7.

Hope that helps.