Comments get assigned to the wrong post.

This has been happening to me the past few days as well. I haven’t changed anything that I’m aware of.

Hope someone can help us fix this!

I think I fixed my problem.

I had added some extra code to single.php that should have gone in the loop. Removing this code seemed to have solved the problem. The actual code removed may or may not be relative. It’s meant to create a list of related posts based on tags at the end of the article. I’ve included it below for the sake of curiosity.

<?php
//for use in the loop, list 5 post titles related to first tag on current post
$tags = wp_get_post_tags($post->ID);
if ($tags) {
  echo '<strong>Related Posts:</strong><ul>';
  $first_tag = $tags[0]->term_id;
  $args=array(
    'tag__in' => array($first_tag),
    'post__not_in' => array($post->ID),
    'showposts'=>5,
    'caller_get_posts'=>1
   );
  $my_query = new WP_Query($args);
  if( $my_query->have_posts() ) {
    while ($my_query->have_posts()) : $my_query->the_post(); ?>
      <li><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></li>
      <?php
    endwhile;
  }
  echo '</ul>';
}
?>

@katrinaneufeld : Use this code piece ..this should work fine..

<?php
//for use in the loop, list 5 post titles related to first tag on current post
$backup = $post;  // backup the current object
$tags = wp_get_post_tags($post->ID);
if ($tags) {
  echo '<strong>Related Posts:</strong><ul>';
  $first_tag = $tags[0]->term_id;
  $args=array(
    'tag__in' => array($first_tag),
    'post__not_in' => array($post->ID),
    'showposts'=>5,
    'caller_get_posts'=>1
   );
  $my_query = new WP_Query($args);
  if( $my_query->have_posts() ) {
    while ($my_query->have_posts()) : $my_query->the_post(); ?>
      <li><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></li>
      <?php
    endwhile;
  }
  echo '</ul>';
  $post = $backup;  // copy it back
  wp_reset_query(); // to use the original query again
}
?>

The 1st line and the last two lines that are added are the solution to the missing puzzle.

The code below for related posts works fine on my blog, since 2.7 up to the current 2.8.1 – you may want to give it a try. I switched to it, after having the same problems with comments being assigned to a different post.

<?php
	$original_post = $post;
	$tags = wp_get_post_tags($post->ID);
	$tagIDs = array();
	if ($tags) {
		$tagcount = count($tags);
		for ($i = 0; $i < $tagcount; $i++) {
			$tagIDs[$i] = $tags[$i]->term_id;
		}
	$args=array(
	'tag__in' => $tagIDs,
	'post__not_in' => array($post->ID),
	'showposts'=>5,
	'caller_get_posts'=>1
);
$my_query = new WP_Query($args);
if( $my_query->have_posts() ) {
	echo '<strong>Similar Posts</strong>';
	while ($my_query->have_posts()) : $my_query->the_post(); ?>
		<ul>
			<li><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></li>
		</ul>
	<?php endwhile;
	}
	}
	$post = $original_post;
	wp_reset_query();
	?>

What happens to me seems to be different: Everyday in one or two posts appear comments dated about one year before. Only solution for me so far has been opening post by post and looking for comments not related to it and with an older date.

Any solution for that?

Thanks a lot 7sins this fixed my problem as well.