If you dont like the karma system, then dont use it, simple enough. Its mostly of use on the buy sell section to be honest - eg, if someones a dick, and enough people have rated down their username, I probably wont trust my money with them.
Whats more useful for transactions is the feedback thing, which people should use more often. Even I forget. Demand it from your buyers and feel responsible to give details of that transaction when you yourself buy. People do occasionally get screwed on this site, so dont be a statistic.