Took me a bit to wrap my head around the regex and capturing groups. It’s powerful once I understood it. Here is my adapted solution.

Call the partial in my `layouts/post/single.html` template like

```
{{ partial "header-link.html" .Content }}
```

The partial is defined as

```
{{ . | replaceRE "(<h[2] id=\"([^\"]+)\">)(.+)(</h[2]+>)" `${1}<a class="header-icon-link" href="#${2}"><i data-feather="link"></i></a> ${3}${4}` | safeHTML }}
```

Which will take take html like this

```
<h2 id="text">Text</h2>
```

And convert it to this

```
<h2 id="text"><a class="header-icon-link" href="#text"><i data-feather="link"></i></a> Text</h2>
```

Then feather.js will convert `<i data-feather="link"></i>` to an svg icon