This question is to know if I need to keep a backup of my forked Gists or not.
There's a similar question that addresses What happens to the forks when deleting the original repository?.
So, basically, I want to know what happens to my fork if the original Gist is deleted. Do I still get to keep the forks when they were made from a public Gist (like in GitHub repos)?
I've contacted support and the answer from Robert Norrie (GitHub Support) was
If the original gist is deleted, any forks simply lose their fork relationship with the original and become a standalone gist. They don't get deleted.
So, no need to do the backups.