What I'm looking for now is Visual Evidence of this thing's existence. Everything I've got together so far is below, and in the comments.
It was about a Puritan, Victorian-era society trapped in a whale-like creature. I remember it being called "Gutsworld", but upon looking it up, all I could find was a Wrestling Organization by the same name.
Civilization inside whale and related search terms came up with nothing.
It was a Graphic Novel, available to order on the internet, I think. Earlier than 2017 but after 2013, at least that's when I came across it; might have been made earlier.
Here is the only living mention of it on any site I can find. The link on the webpage takes me to a dead IP address. I put this into the Wayback Machine and it came up with this (I'm not very experienced using this, so if anyone can get more info out of it that would be a huge help).
Apparently the reason it's a dead IP is because Newsarama, the site that hosted these forums, was bought and has shut down the forum service. They deleted the entire archives of the forums when they did so.
So, it would appear there is more to this tale than meets the eye.