Looking in to this a little more, you're going to have to make the existing process of cleaning up the spacers a bit more complex. Right now, this process is handled by `WYMeditor.editor.xhtml` with a single call to remove `br` tags in the body. 

I would create a `removeBlockingElementSpacers` function (that should probably go right under the `spaceBlockingElements` call) that then gets called by `xhtml` in the same place the current, simple, call goes. Then, in addition to removing `br` tags in the body, you should clean up those tags. I'm not sure, but you might be able to simplify things by doing a selector on the `_moz_editor_bogus_node` property, but that might not work. Maybe we should consider adding a `class="wym-blocking-element-spacer"` to all of those `br` elements so that they're easier to remove?