No comment and yet last comment time shown

I think this is by design, and is used so that the last comment timestamp ordering works even if there are no comments (such as for tracker). I agree this could be misleading data, but this is how it works intentionally as far as I see. You can debate it for a change in Drupal 7 as far as I can tell.

The code which sets the comment time when a node is being inserted even before a comment is possible to be added:

/**
 * Implementation of hook_nodeapi().
 */
function comment_nodeapi(&$node, $op, $arg = 0) {
  switch ($op) {
    // ...
    case 'insert':
      db_query('INSERT INTO {node_comment_statistics} (nid, last_comment_timestamp, last_comment_name, last_comment_uid, comment_count) VALUES (%d, %d, NULL, %d, 0)', $node->nid, $node->changed, $node->uid);
      break;
  }
}

By the way you can spot this non-real-comment data (and filter out such data in views) by checking that the comment count is zero. That means there were no actual comments yet.

@gremonty: this seems to be by design. As you didn't post another comment on #352901: Last Comment Time shown in Views even if no comment, I presume you eventually figured out how to get Views to distinguish nodes with comment_count === 0.

If, as Gábor suggested, you still want this changed in D7, please re-open.