I don’t feel this is very much an issue with the karma system, just a problem with “mean people suck”. No matter what technical system is in place, there will probably be some ways for people to be meanies—sending lots of nasty personal messages from behind a TOR proxy, for instance. The fact that in this case they decided to (ab)use the voting system is incidental, and a solution need not involve making any dramatic changes to how the voting mechanisms work.
I don’t feel this is very much an issue with the karma system, just a problem with “mean people suck”. No matter what technical system is in place, there will probably be some ways for people to be meanies—sending lots of nasty personal messages from behind a TOR proxy, for instance. The fact that in this case they decided to (ab)use the voting system is incidental, and a solution need not involve making any dramatic changes to how the voting mechanisms work.