WP is confusing threaded comments with non-threaded comments

I’m trying to write a theme with threaded comments. I put

<?php if ( is_singular() ) wp_enqueue_script( ‘comment-reply’ ); wp_head(); ?>

in the head section, enabled threaded comments 10 levels deep in Settings, and I am using the comments.php file (unaltered) from Kubrick.

But why do I end up with this? Specifically, this non-threaded comment and this threaded comment show up as the exact opposite of what they should be; that is, the threaded comment should appear in the middle of the other comments and the non-threaded comment should be at the end of the entire conversation.

Here is all the code I have for now, just in case something else is getting in the way. What am I doing wrong?

Thanks in advance.