Ability to destroy some amount of someone's Karma by sacrificing some of your own.

No to a general destruction of karma. That would be nearly pointless. Especially since it is (more or less) free to downvote comments.

i would like the ability to up or downvote an individual comment more significantly that 1 karma but with a cost. Either a limitation of how often you can do it or at karma cost to self. The difference between 'yeah, decent' and 'Wow! That was the most fascinating thing I read all week!'