Up until just a decade ago, maybe less, we knew a commentator as one who delivered the news or had some views and opinions on a news story and would share those views via their chosen media.
All that has changed. Now everyone has the ability to leave online comments of their own. In fact, a measure of how good or interesting a story has proven to be is based on the number of comments people have made on it. Now anyone, if they want to be, can be a commentator. Authority and validity may be a question but that’s another story.