comment_on_draft
comment_on_draft is an action fired whenever someone attempts to post a comment on a post that is in draft status. Comment spammers may try to blindly spam entries, without checking to see if they are published entries, so you can use this hook to take extra steps to punish them for this behavior (like blacklisting their IP).
The ID of the draft post they attempted to comment on will be passed as the only parameter.
Context:
File: wp-comments-post.php
if ( empty($status->comment_status) ) {
do_action('comment_id_not_found', $comment_post_ID);
exit;
} elseif ( 'closed' == $status->comment_status ) {
do_action('comment_closed', $comment_post_ID);
die( __('Sorry, comments are closed for this item.') );
} elseif ( 'draft' == $status->post_status ) {
do_action('comment_on_draft', $comment_post_ID);
exit;
}
This hook is an action which means that it primarily acts as an event trigger, instead of a content filter. This is a semantic difference, but it will help you to remember what this hook does if you use it like this: add_action('comment_on_draft', 'your_function');