Despite the fact that it runs in the community pages, it doesn’t strike me as valid Markdown.
Hmmm. I was just about to reflexively protest that it’s totally orthodox Markdown, but then I noticed that “upload:” part of the image URL. I must say I don’t know what the heck that is or where it came from.
I went back to my base to look at the line there. It wasn’t what showed up in my earlier post. HERE is the exact code I’m using. (Well, was using until a few minutes ago. See down below.)

If that doesn’t get rewritten when I post, you should see the line beginning with an exclamation point, then a bit of descriptive text (“Pooh”) inside square brackets, followed by an https link to an image on Imgur. Here’s the result (and in the preview pane it’s working:

Completely valid, at least per the Markdown “Bible”. Yet doesn’t work in my Base Guide.
But I tried something: I removed the empty quotation marks after the URL. Those are legal per John Gruber, but apparently Airtable’s Markdown parser doesn’t like them. When I eliminated the quotation marks, eureka, it works!!
THANKS, BILL.
