The Markdown engine converts the short filename into an actual HTML link that points to the file. I’m sorry, it’s not possible to switch back to the previous behavior.
The easiest solution is to copy the URL of the image after posting.
This means that what was great is broken for me now, and I don’t see any easy solution. (Devoid of a lot of clicking.)
I like to host my images in discourse so that when I post on wordpress, and it links back to discourse via wp-discourse plugin, there’s no duplicate image storage.