This bug was reported to mkdoc-dev on 18th April 2006: https://lists.webarch.co.uk/pipermail/mkdoc-dev/2006-April/000326.html
Images that have titles that match the title of a link component have a bug in the way their links are constructed.
For example, on a site with http://www.example.org/ for the public and http://users.example.org/ for admin:
Upload a image titled “example”
Add the text “example” to a text component
Create a /about/example/ document
Add a link component with the title set to “example” and the uri to “/about/example/”
Then in the public interface everything should be fine, the text “example” and the image example both link to http://www.example.org/about/example/
But when in admin the text links to http://users.example.org/about/example/ but the image links to http://www.example.org/about/example/ — ie the public interface not the users interface.
There is nothing in the template that contains the domain name so this bug must be in the code.