I don't see a need for any of it really. Aside from all the possible crap to come from ghosting, why go through the process of adding in the other options?

In a PM I want responses, so why limit them to what they can and can't comment on? If I don't want Jack, John, Jimmy, or Martha to comment, it'd be easy to just message the preferred commenter. 

And edits are easy as mentioning the needed edit and where it should to, or copy/pasting and making the edit that way.