Behavior of **a*_b**

Looking at https://johnmacfarlane.net/babelmark2/?text=**a*_b**

There seems to be disagreement in the wild:

CommonMark wants **a*_b** to render as

<p><em><em>a</em>_b</em>*</p>

Whereas lots of the established players render as:

<p><strong>a*_b</strong></p>

Does this double <em> even make sense conceptually, it seems like some weird HTML to me.

I wouldn’t say there is some kind of super consensus on this…

Like everything else with Markdown, it is indeterminate.

Also this is valid HTML5…

<!DOCTYPE html>
<html lang="en">
<head>
<title>test</title>
</head>
<p><em><em>a</em>_b</em>*</p>
</html>

https://validator.w3.org/nu/#textarea