@ Thudlow just above …
An unfortunate side effect of Discourse being so CSS-driven is that stuff looks different under different themes. You can only know how your post looks under the theme you’re using.
Discourse and its themes are also device-aware = phone vs tablet vs PC vs ???. So you can only know how your post looks on the device(s) you’re willing / able to test it on.
Another issue is that websites themselves are free to deliver different content to phones than to tablets than to PCs. or to different brands of browsers. Which is to say my #3 is a moving target depending on which device is doing the viewing.
While composing this post on my PC I tried this page on my phone, a Samsung Android using Chrome. The 2-cats pic does display on my post and on yours.
At least some phones have a browser setting to enable or disable inline image downloading. That may be your issue.