This is known and currently working by design, the idea is that the image is only uploaded when the ticket is created so pagure doesn't know what the path to the file will be, so it uses this <!!image> as a placeholder which is replaced with the correct links when the ticket is created.

Oups, look like this comment was for #4858 :)

This ticket is likely python-bleach cleaning this a little too aggressively. Something to look into but should be a simple fix.