This one can be easily tested in the CKEditor demo page:
1. Simply load the following HTML on source view and move back to the WYSIWYG view:
2. Put the caret at the beginning of the "test2" paragraph.
3. Hit BACKSPACE.
Switch back to the source view to check the code. You'll have this:
<h1>test<span class="Apple-style-span" style="font-size: 12px; font-weight: normal; ">test2</span></h1>
The additional <span> tag has been added to the DOM.