Empty HTML comments are rendered in the editor

[oandregal]

Related #47212 #38984

Description

Empty HTML comments are rendered in the editor, though they should not be.

Step-by-step reproduction instructions

• Add the following code to the single.html template of TwentyTwentyThree:

<!--
        title: Title for the template or part
        area: related-area
-->

• Go to the site editor and navigate to the single.html template. This is what I see:

• The front-end doesn't render the HTML comment:

[bobbingwide]

I'm not sure what exactly is meant by "empty", but my experience is that the HTML comment is rendered inside a paragraph.

Input was from a template starting

<!-- An HTML comment -->
<div class="WP_DEBUG">Fizzie front-page.html</div>

On the front-end this is rendered as is.

In the site editor the comment gets wrapped in a paragraph tag.

If this template is Saved the unwanted paragraph remains.

[bobbingwide]

In other instances <br /> tags may be added where there were new lines in the original template HTML.

<div class="WP_DEBUG">Fizzie front-page.html
<!-- Comment in div -->
</div>

becomes

<div class="WP_DEBUG">Fizzie front-page.html<br />
<!-- Comment in div -->
</div>