Experiences with adding Nonces to the comment form

I haven’t done this personally, but it would be pretty easy. If you are building your comment form manually, just before the end of the </form> put:

<?php wp_nonce_field( 'comment_nonce' ) ?>

Then, just hook into the pre_comment_on_post action which fires when you submit a comment:

add_action( 'pre_comment_on_post', 'my_verify_comment_nonce' );

function my_verify_comment_nonce() {

    check_admin_referer( 'comment_nonce' );

}

If you want to just hook into the standard comment form that Twenty Ten uses (comment_form()) then you could instead hook into comment_form like so:

add_action( 'comment_form', 'my_add_comment_nonce_to_form' );

function my_add_comment_nonce_to_form() {

    wp_nonce_field( 'comment_nonce' );

}

Not tested, so let me know if you have any issues!