It sounds good, although it would encourage commenting even more - most of people who actually comment in the first place got a little disorder which means: "I didn't understand anything at all what you said so I gotta drill my point over and over again like a broken record"
I like it in principle, but I've gotten into a few comment threads with people who just HAVE to have the final word, or just act like a d*** in general.
I'd combine this with another wished-for feature. I'd like the option to spend Xper points to find out who certain anonymous posters are. Want to block this anonymous d***? We won't tell you who it is, but we'll put the block in place for 1500 Xper points.
This would allow long time serious posters to stop being hassled from some of the fly-by-night anonymous f***wits we seem to attract so often.