Why does WP automatically add a or at the end of each comment?

I’m 95% sure WordPress does! The callback is controlled by my theme yes, but there is no </li> in that yet one is being outputted!

I’m not entirely sure it’s a problem. I think it is intentional on the part of WordPress.

I can show you an example. Take a look at the custom callback function mytheme_comment on this page:

http://codex.wordpress.org/Function_Reference/wp_list_comments

You’ll see a tag is opened by line: <<?php echo $tag ?> <?php comment_class(empty( $args['has_children'] ) ? '' : 'parent') ?> id="comment-<?php comment_ID() ?>">. However the tag isn’t closed which indicates it is closed automatically by WordPress.

You’ll be able to replicate on a fresh install, default theme, no plugins activated.

Now do you see what I mean? My question is why does WordPress do it this way?

Yes I can and it isn’t a problem, it’s intentional. I just had an answer over at Stack Overflow if anyone is interested

http://stackoverflow.com/questions/19161310/why-does-wordpress-automatically-output-a-closing-li-or-div-tag-at-the-end-of-ea