So the problem is when we would like to copy HTML source from an external editor which contains a images with full paths Moodle will remove the links and shows as deleted.
When you add an image in the editor the source code looks like this:
<img src="[my site URL]/draftfile.php/5/user/draft/92639947/timon.jpg" alt="Description">
But when you save it, it turns something like this:
<img src="[my site URL]/pluginfile.php/243/mod_page/content/9/timon.jpg" alt="Description">
So draftfile become a pluginfile and that causes the problem if we want to copy HTML source code from an external editor.
The solution is that we have to use the source code that moodle displays and not the one that the editor shows.
Thanks to JM Casas providing this workaround in the moodle forums.