@NEA Have you tried using
<span> instead of
<div> or Markdown Extra?
<a href="https://www.website.com/" rel="nofollow"><img alt="ALT_TEXT" src="/site-blog/user/pages/01.blog/hero-classes/unsplash-overcast-mountains.jpg"></a>
See here for explaination: How can I wrap my markdown in an HTML div?
And according to another answer, Markdown Extra does support
<div>. Markdown Extra is supported by Grav (see Grav’s Mardown docs):
Grav ships with built-in support for Markdown and Markdown Extra. You must enable Markdown Extra in your
system.yaml configuration file.