If I try to add the IMG prefix and suffix to image source links, I can insert the link into posts but not the image itself. What am I doing wrong?
From your description, I'd guess that you aren't using the HTTP address of the
actual image. The important thing is that the URL must point to an image file, i.e. a filename ending with an image type extension such as .JPG , .JPEG, .PNG etc.
It's a common problem that people try and use the image
page rather than the file. For instance, the link below is to a picture hosted on Flickr:
https://www.flickr.com/photos/suzi54241/41953844760...but that is
NOT the image, it's a page containing the image. The actual filename is:
https://farm2.staticflickr.com/1776/41953844760_109ae72179_b.jpgNote the difference, especially the ".jpg" extension on the second URL. The first link will not work between IMG tags but the second one will.
Hope that's not too techy!