The presence of positive karma and negative karma is necessary for interaction between members by giving positive karma to good posts and negative karma to spam. The problem is that members are unable to see who gave them negative or positive karma and moderators cannot monitor all cases. This is somewhat difficult.
Of course, the karma system has good features to improve the quality of posts and influence the rank of members, but as is always the case, the system is abused, whether by exchanging positive karma between some members or sometimes using negative karma for revenge.
I do not know how to stop such cases, but as I heard, there is a new update to the Karma system, so we hope that there will be some new features that help reduce these cases.