Hi, I don't seem to have the option to post an image.
Mac Sierra v. 10.12.6
Safari and Chrome have the same issue.
I have the Horizontal Line option, then Insert/Edit Link, then Align Left. No Insert Image.
You got to have a certain rank prior to being able to upload images to site... This is based on post count, etc.. An alternative until you reached said rank is use a 3rd party hosting site and provide link inside message. Hope this helps.