Actuallly you can get around this limitation… by writing an HTML comment with enough words in the body of the post like:
<!--
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed bibendum pharetra finibus. Fusce sed ligula et leo elementum viverra quis.
-->
So if you really want this feature, you can write a theme component to fill the editor with an HTML comment by default.
However, this is a really strange request, and few people would do this. In Chinese forums, we usually type “RT”(It is an abbreviation of “As the title”) in the text to indicate that the text and title are consistent. I think most cultures should have similar expressions
Moreover, it doesn’t look good, and it makes people feel like there is a bug.