Is it possible for the post creator to rotate an uploaded image within the Discourse application?
Perhaps in the same way that they can change the size with the
buttons.
In the Arduino Forum, users frequently post photographs of hand-drawn schematics that are in the portrait orientation, e.g., when they would be easier to read in the landscape orientation. How to edit the post to correct the orientation might be easier to explain to the user than explaining how to change it in another application or explaining how to create the photo in the correct orientation in the first place.