When either creating a new thread or editing one, I do not see a way to expand the area of the message box (where this message currently appears). I searched and maybe this has been reported or perhaps it is a known issue and I should be using a different browser.
In Chrome, I click back in the box and it selects the image, it does nothing to expand the test box. I have been bothered by this since posting this because this made the forum more difficult for me to use. Today, I inadvertently moved the cursor to the right after selecting the image and the text box expanded automatically. What a relief!