It happens when using the  Markdown convention in a code block and then using the same code outside of the code block to actually display the image. It happens after about 5 minutes once Discourse downloads the hotlinked image.
For the record, I faced the issue when trying to illustrate this:
To circumvent the problem, I used Ő° (armenian small letter ho) instead of h (latin small letter h) in the https part. Since they are recognized as different characters, it doesnât trigger the URL replacement.
Thanks to Unicode Utilities: Confusables
great description. Our logic skips detecting images in a codeblock. But if there is a real image somewhere with exactly-identical markdown, then our actual find/replace code isnât robust enough to avoid the codeblocks.
Itâs not going to be trivial to fix, but for now Iâve added some failing tests so that weâre tracking the issue:
