- Create a course with two topics
- Add an activity in each topic
- Edit the description of the first topic
- Switch to HTML mode then back to WYSIWYG mode (don't actually enter anything in the text field)
- Go back to the course and you'll notice extra space under topic 1 (this is because atto has inserted <p><br /></p>)
- Go back to the topic description, switch to HTML mode, and delete everything
- The white space is still there
The only way I found to remove it within moodle is by using the "plain text" text editor.