//Get your latest post in a category:

$args = array('cat' => 4, 

                   'showposts' => 1, 

                   'orderby' = 'date');

query_posts($args);



if (have_posts()) : while (have_posts()) : the_post();

  $args = array('post_ID' => $post->ID, 

                     'status' => "approve", 

                     'order' => 'ASC', 

                     'number' => 1);

  $comment = get_comments($args);



  if(!empty($comment)) {

    ?>

    <a href="<?php get_comment_link($comment[0]->comment_ID) ?>"><?php the_title(); ?></a>

    by <a href="<?php $comment[0]->comment_author_url; ?>"><?php $comment[0]->comment_author; ?></a>

  <?php } else { ?>

    <a href="<?php the_permalink() ?>"><?php the_title(); ?></a>

    by <?php the_author() ?>

<?php

  }



endwhile; endif;