How do I make the superscript/subscript style in running headers? I have used below CSS properties, but it does not works.

CSS:
@page :right {
@top-right
{
content: string(heading, first);
font: 8pt "MyriadPro-It", serif;
margin-top:49.8pt;
vertical-align:top;
border:0px solid;
}
}

h1{display: block; font: 12.5pt/14pt "MyriadPro-Semibold", serif;margin: 20pt 0 0pt 0;font-weight:bold;text-align: left; page-break-after: avoid;string-set: heading content(text);}

HTML:
<h1>Modern Aspects of ³¹P NMR Spectroscopy</h1>

CSS named strings only capture the text content, not the markup or styling; capturing superscripts and other formatting markup requires moving a complete element to the margin box.

Is there any update to running headers accepting formatting markup?

I do have a dedicated elements for my running headers, but they still do not apply my CSS formatting markup.

HTML document:

<section data-number="38" id="ch009.xhtml.preliminaries">
<p class="verso_header">9&#160;&#160;&#160;The Article with Substantives</p>

<p class="recto_header">9.1&#160;&#160;&#160;Preliminaries</p>
<h2 class="SIL01LevelHead" data-number="38" id="ch009.xhtml.sigil_toc_id_66">9.1 Preliminaries</h2>

<p class="SIL_Para-1">Porter distinguishes two uses of the article with substantives: the “particular” use and the
“categorical” use. “When the article is used, the substantive may refer to a particular item, or it may
represent a category of items” (1992:104).</p>

CSS:


@page {
@top-left {
content: normal;
}
@top-right {
content: normal;
}
}

p.verso_header {
font-family: "Charis SIL", "Galatia SIL";
string-set: chap-title content();
visibility: hidden;
height: 0;
}
p.recto_header {
font-family: "Charis SIL", "Galatia SIL";
string-set: section-title content();
visibility: hidden;
height: 0;
}