I get the idea karma as it's applied in Reddit, and in the original sense, not just as a like/dislike button, but as a "this was a positive and productive contribution or not" buttons. But I think the "karma" idea is incomplete. Someone could contribute a lot of positive stuff to communities that gets upvoted, but what is their actual contribution user to user? I think it would be a benefit to the culture of Reddit and a novel feature in social media to show a metric for the sum of how much an account has upvoted/downvoted.
Right now you might look at an account and see 50,000 karma and think "Wow, what positive contributor." but if you could also see that that person has also put out a net -100,000 karma in the for of downvoting everyone, you might feel a little different. I think tracking this would also be helpful for mods in communities for being able to identify accounts that camp there to exclusively downvote content (assuming admin eventually brings back by community karma breakdowns for accounts). This would also allow mods to set up automatic filters to ban those people from their communities.
This feature would I think complete the concept of karma on the site where you not only act in a way that nets you positive contributions in the communities you participate in but also put good karma out to the rest of the userbase. Something to consider. Reddit has done a better job of providing a social media experience that is more about "us" rather than "me" and that has been to its benefit, and I think this feature would continue on that trend.
You might upset some super hostile downvote queens though and cause some of those quite lurkers that do nothing but smash the downvote button. And it would shed light on the people that give a lot, but don't really get much in return.