I have a meta-question - since you're submitting from kbin.social, are you separately uploading the image before submitting? On Fedia.io (another kbin instance), if I go to submit an image directly I can't include body text with it so I'm just wondering how you're getting that!
I upload my files to catbox.moe (a file hosting service) first, and then submit that as a link through kbin.social. It lets me include body text with a link.
I know on some instances, when you view media from another federated instance, the media shows up as if its hosted directly on that instance instead of where it's actually hosted.