Okay, well it seems pretty clear then. “Do not parse or show” :
http://talk.commonmark.org/t/jekyll-style-do-not-show-sections/918
This is not quite a “Do not parse, but show” island. But rather this is “Do not parse or show” island. We need a different syntax for those who wants a “no parsing but show in html”.
The “Do not parse or show” will be useful for comments, application specific metadata, etc…
It is recommended to have a implementers guide for a general concensous for optional metadata interpretion, so that most simple documents can have readable metadata (e.g. stripped down YAML). But the core of common mark will not include metadata interpretation (could have a hook thought).