When a code block contains syntax for an image, lemmy seems to replace the image’s url with a proxied one.
This instance’s web UI’s preview displays the original url correctly. The proxied url is also distributed trough federation, so users on other instances or for example Piefed should also see the lemmy.ml url in the example below.
This behavior is unexpected, as the contents of a code block should not be parsed as markdown, and thus no image should be displayed and no requests to the server should be made.
Example:
I entered “https://media.piefed.zip/posts/bT/UD/bTUDGZRAcKZdXyO.png” as the url in the following code block in the web UI: 
Lemmy UI version: 0.19.17
Lemmy backend version: 0.19.18-beta.0
Yes it does.
Release notes
That doesn’t explain why urls in code blocks are rewriten as well. When the image is surrounded by backticks, it shouldn’t be parsed but rather displayed verbatim as the code block’s content.
That’s a fair one, could write a bug for it on GitHub
Sorry, but could I ask you to file the issue? I would rather not associate my social accounts with my real identity.
I probably should have filed an issue to begin with.