This is an extension of #851 because that issue seems to be closed/old.

The current state that left off was "Comment parentItem Comment". This still doesn't make full sense because "CreativeWork comment Comment" is essentially the inverse edge of this (I don't know if that was the intention but it's very close semantically). If the top level item that the comment is attached to is not a Question/Answer (let's say a DiscussionForumPosting or a VideoObject or something), there's no way to specify it.

I am proposing expanding the range of parentItem to be CreativeWork.