The commenter levels range from 1 to 8. This level goes up by you creating engaging and interesting comments on peoples hubs. The score goes into your overall Hubscore and it helps define how active you are with Hubpages to a degree. Now it is noted that if you stop commenting or if you leave short one word or short comments you can have your comment level reduced. While many people take it as a sign of your commitment to other Hubbers I don't think of it as much, because more people like reading and might have more time to leave comments then others.