<div>
    {# !hide This should never appear in HTML #}
    {# This should become an HTML comment #}
    {% comment "!hide" %}
    This block should never appear in HTML
    {% endcomment %}
    {% comment "!hide todo" %}
    Block with note also hidden
    {% endcomment %}
    {% comment %}This block should become an HTML comment{% endcomment %}
    <p>Visible content</p>
</div>