This is so that users can use the new rendering and new WYSIWYG editor by default since they are now good enough.
Single enter key should go out of headings into a paragraph
Use the new WYSIWYG to edit object properties that accept rich text
Hitting return twice at the end of a heading doesn't go out of the heading in IE
Provide tabs allowing to switch between WYSIWYG and WIKI when editing a page
Allow attaching new files when creating links
Support automatic inline editing with new rendering
Allow setting the default rendering syntax wiki by wiki