Display comments of users on single page

You can use the get_comments function to retrieve comments from a specific user.

$comments = get_comments( array( 'user_id' => 1 ) );
foreach( $comments as $comment ) {
    $post_id = $comment->comment_post_ID;
    $post = get_post( $post_id );
    setup_postdata( $post );
    echo '<a href="' . get_permalink() . '">' . get_the_title() . '</a>';
    echo $comment->comment_author . '<br />' . $comment->comment_content;
}