I just registered on the forum and wen’t through with the discobot tutorial, but it seems as web images don’t work with drag’n drop and neither with the upload button, it simply pastes in the link to the image.
Drag’n drop and upload works correctly with images being uploaded from my computer.
I’m using Google Chrome version 66.0.3359.139
Adding the missing markup around the url:
!(url) makes it work, so it’s probably just that for some reason it doesn’t get added automatically for web images?