I agree that it would be interesting but I suspect that just as “total karma” is a combination of “comment quality” and “time on LW” (where for most purposes the former is more interesting, but the latter makes a big difference), so “percent positive karma” is a combination of “comment quality” and “what sort of discussions one frequents”, where again the former is more interesting but the latter makes a big difference.
I agree that it would be interesting but I suspect that just as “total karma” is a combination of “comment quality” and “time on LW” (where for most purposes the former is more interesting, but the latter makes a big difference), so “percent positive karma” is a combination of “comment quality” and “what sort of discussions one frequents”, where again the former is more interesting but the latter makes a big difference.