A commenter is someone who makes isolated comments. These days, the word most often refers to people who post comments on blogs and news websites. A commentator is someone who provides commentary. The term usually applies to professionals in sports broadcasting or television news. Commentators don’t just make one comment; commenting is what they do.
The difference between these words corresponds to the difference between a comment and commentary. A comment is an isolated remark, while a commentary is a series of remarks, explanations, and interpretations.
Examples
When we talked a bit about reducing food-related waste, one commenter mentioned that her main frustration was over produce packaging, especially organic produce. [Care2]
And when it was revealed that Channel Ten was not going to use her as an AFL commentator this season, there were plenty who relished another opportunity to stick the boot in. [Sydney Morning Herald]
The scoop artist is edlharris, a frequent and often wise commenter in this blog.[Washington Post]
Commentator Glenn Beck and others have repeatedly drawn parallels between Egypt and the Wisconsin protests. [Christian Science Monitor]
Now though it has had to be moderated after it was hijacked by commenters who mocked both Natasha and the manner of her death heartlessly. [Telegraph]
Many fans and NBA commentators have said that we are witnessing a point guard revolution. [Yahoo! Sports]