I edit a page in WYSIWYG-mode and insert e.g. 3 blank lines in the text (Spaces_WYSIWYG.png). When I view the preview, there is only one line break, but no blank line (Spaces_Preview.png). The same in the final page. When I open the WYSIWYG-editor again after saving, the page looks like in the preview, without the blank lines. Only in the markup editor, the blank lines are still present.
This means that the WYSIWYG-editor is not really WYSIWYG.