Remove metadata matching criteria from a comment. You can match based on the key, or key and value. Removing based on key and value will keep from removing duplicate metadata with the same key. It also allows removing all metadata matching key, if needed.
<?php delete_comment_meta( $comment_id, $meta_key, $meta_value ); ?>
<?php // Delete all metadata with the key 'my_meta_key' for comment ID 5. delete_comment_meta( 5, 'my_meta_key' ); // Delete metadata for 'my_meta_key' only where the meta_value is 'foo'. delete_comment_meta( 5, 'my_meta_key', 'foo' ); ?>
delete_comment_meta() is located in