Without apparent pattern, remote PNG images are not rendered in forum discussions. Instead the URL (not a preview) is shown instead.
It happens frequently enough that one of my postings (that has 2 remote images and no other links) was awarded a “Popular Link” badge today. One image had 46 clicks and the other had 50 clicks but the thread has 1.7k views. So it showed the images instead of the links for most of the time.
We have a large number of GUI elements and dialog captures for our (self-hosted MediaWiki) documentation. Rather than have redundant uploads clogging up the Discourse host, we want to just link to the remote location for that image on our MediaWiki server.
Most of the time, this works fine. (Although it is frustrating that the Scaling interface isn’t available in the Discourse editor GUI.) However, Discourse unpredictably shows the URL. When I “quoted” the message, the preview showed the URLs and still did so after hitting the “Create Topic” button. However, repeated views sometimes show the image, sometimes the URL.
A message about this problem (linked to an example of an offending message) was posted to our Feedback category.