Also I struggled to post the image because my go-to image posting method for kinja was to 'open image in new tab' and then copy/paste the URL. I can't find where to do that with the new commenting tool. For the time being I just saved it to my computer and uploaded it, but I really like the copy/paste image URL method cause it saves me the trouble of clearing a bunch of cat gifs out of my downloads folder.
I tried drag and drop as suggested one post below mine but that didn't work either! Maybe it was a file size thing or something that prevented the drag & drop.