The closing <div>s inside HTML comment blocks appear outside the
comment which makes the exported HTML invalid. For example:

  #+title: Stray div demo

  Hello.

  #+html: <!--

  * Heading
  ** Subheading

  #+html: -->

  Goodbye.

Produces this HTML (cleaned up to make it easier to read, see
attached for original files):

  <p>Hello.</p>
  <!--
  <div>
  <h2>Heading</h2>
  <div>
  </div>
  <div>
  <h3>Subheading</h3>
  <div>
  -->
  <p>Goodbye.</p>
  </div>
  </div>
  </div>


Emacs  : GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38, cairo version 1.18.0)
 of 2024-03-08
Package: Org mode version 9.6.15 (release_9.6.15 @ /home/jm/.local/share/emacs/30.0.50/lisp/org/)