Ah. There's a Jekyll SEO plugin installed. That explains why nothing worked.

Author: dylanbeattie

codewithrockstar.com/_config.yml

@@ -1,9 +1,18 @@
 title: Rockstar
-description: Tommy used to work on the docs.
+tagline: Tommy used to work on the docs.
 theme: just-the-docs
 
 url: https://codewithrockstar.com
 
+defaults:
+  - scope:
+      path: ""
+    values:
+      title: Rockstar
+      tagline: Tommy used to work on the docs.
+      image: /images/rockstar-og-image.jpg
+      description: "Rockstar is an esoteric programming language based on the ‘lyrical conventions of 1980s hard rock songs and power ballads.’. It was created by Dylan Beattie in 2018."
+
 color_scheme: darkstar
 
 include:

codewithrockstar.com/_includes/head_custom.html

@@ -6,10 +6,3 @@
 <!-- Fathom - beautiful, simple website analytics -->
 <script src="https://cdn.usefathom.com/script.js" data-site="XEFKZVQW" defer></script>
 <!-- / Fathom -->
-
-<meta name="description" content="Rockstar is an esoteric programming language based on the ‘lyrical conventions of 1980s hard rock songs and power ballads.’. It was created by Dylan Beattie in 2018." />
-<meta property="og:url" content="https://codewithrockstar.com" />
-<meta property="og:type" content="website" />
-<meta property="og:title" content="Rockstar" />
-<meta property="og:description" content="Tommy used to work on the docs." />
-<meta property="og:image" content="/images/rockstar-og-image.jpg" />