Like this the system is putting a lot of weight on the users with more Karma... and I am guessing there are "many" more users with less than 1000 compared to those with more? Some people may never have a chance to state their opinion like this.
Rather, the opposite approach might work? Users with more than X karma can completely remove some comments, and say if your comment has been removed, you are not allowed to comment again for a specific period of time. If you post x rejected comments in a row then potentially you get banned.
EDIT - maybe a little off topic: another "comment" about comments - I notice you can up vote and down vote comments. I see this functionality sometimes is used to indicate agreement (or lack of) towards a comment. This as far as I cant tell is not the intended functionality, I am unsure however how this can be fixed easily.