Here's the URL in your comment:
https://lemm.ee/api/v3/image_proxy?url=https%3A%2F%2Fimgflip.com%2Fi%2F8zyq0d
If you try to open it directly, you'll see an error, when you should be seeing an image.
I see a couple issues with it.
Firstly, URL contains an image proxy. Now, I'm not sure how exactly Lemmy works and if those are necessary, but my comments don't have those (on most clients you can use an option to see the raw comment text).
Secondly, that imgflip URL leads to a page and not to a direct image, which causes issues. If you link the direct image URL like so:

The result is:

Regarding the podcast you linked, I'm in no way associated with it, if that's what you thought. I'm just using an account on StarTrek.website Lemmy instance because I'm a fuckin' nerd. 🖖