It works for me here

As you can see, it doesn't work for me. I used:

![test image](https://68.media.tumblr.com/avatar_25efafdbc2ba_128.png)

and it created:

<p><img alt="test image"></p>

What code have you used?

Attachments work. OK, that helps. But that's not what I reported, I wanted to link an external image, not upload it.

That does not work in purpose, we do not want to link to images uploaded anywhere on the web.

Good to know. Why?

Also, it's unobvious. Perhaps the Markdown Syntax button under new comment box could lead to a page on pagure documenting which markdown commands are supported and which are not? Alternatively, an error can be displayed when somebody tries to use that syntax, possibly even inline (instead of showing the image, show "linking to external images is not allowed" text).

Good to know. Why?

There was security issues at one point about using the img tag to link to something that wasn't an image (like a js blob or so) and since we're serving the content via the same domain it could be problematic.

Also, it's unobvious. Perhaps the Markdown Syntax button under new comment box could lead to a page on pagure documenting which markdown commands are supported and which are not? Alternatively, an error can be displayed when somebody tries to use that syntax, possibly even inline (instead of showing the image, show "linking to external images is not allowed" text).

Those are good ideas :)

For a start I went with linking to pagure's own markdown documentation and adding a warning there about remote images.

Commit e6d05d6 fixes this issue