1. Create a page in wiki markup:

heading

{children}
h1. heading

2. Save, and edit in wysiwyg.
4. Switch to wiki view and the markup is now:

h1. heading
{children}

heading

3. Save, and edit again in wyswyg
4. Switch to wiki and the markup is now

heading

{children}
h1. heading

5. Edit again, in wysiwyg, and save. The markup is now:

h1. heading

{children}

heading

This adding of whitespace is quite annoying when you are editing a document multiple times, and you have to keep deleting the blank lines added.