it is impossible to measure accurately everybodys work for the community. that's why whe should only improve the calculation formulas for karma if karma is used to measure one's activity and possible rewards are given based to karma.

There will always somebody who's left out. But if majority have justified discounts, I'd say the system works very well.

Of course if something exceptional (must be really awesome) appears and author doesn't get reward that he should, it should be like nobel prize of peace, one per year or something like that.