Images can be posted in two ways:
By using the "img" tag and linking to an image that was uploaded to a third-party image hosting site.
By attaching the image to the post using the image attachments below the reply box.
When you attach an image, it is automatically uploaded to Imgur image hosting. Your post is then automatically updated to include an "img" tag linking to the correct image.
To remove attached images, simply Edit your reply and remove the generated "img" tag from the post.
Note: images are not removed from Imgur in this way. However, the images uploaded to Imgur are not public and can only be seen if the direct link is known.