Why can't anyone post a comment on the CNN or NBCNews websites that have articles?
They know the trolls will run wild. Most any site open to the public has that issue.
You can't do it on the Fox News website either.
They don't want people who disagree with them commenting
I assume it is because their mission is to deliver news. Comments are likely to contain inaccuracies, insults, propaganda and other material they do not consider appropriate for following their mission.