I see that everytime, mostly in Wordpress / Drupal / Whatever templates :
</ol><!-- .commentlist -->
Don't ! here is why :
- No one but an hypothetic future developer will ever need this. But you serve it to the entire world.
- It makes HTML file heavier, since the browser will download these comments. At least use PHP comments.
- With correct indentation, this is most of the times useless. Code is readable enough if correctly indented. It is actually less readable and adds noise.