don't add comments when unbound

This is just a suggestion for a feature and the implementation may not be correct. Take it as an idea if you will.

What this does is avoid adding comments like `<!--unescaped unbound hello.message-->` when the path is unbound and unescaped.

The motivation for this is that 1) these comments are making the life hard in some cases 2) if the path is unbound, I don't think these comments need to be there?

For 1) the case is when I'm making a html editor and I'm using `unbound unescaped` to make the html snippet editable, the extra comments are something extra that I would like to avoid.