Quick follow-up on the Feed Forwarding section from that other post on Jekyll: Turns out, the forwarding in the header of that HTML file did not work as expected. Opening the URL in the browser passed you through to your favorite RSS reader if you have one installed. Feed readers that had already subscribed to the original feed before did not get any updates, though.
So I changed that re-routing to be handled in my
RewriteRule ^feed/?$ /feed.xml [L,NC]
This line fixes the issue. For more information about
.htaccess files and the syntax see the “Apache mod_rewrite Introduction".