I don't think that the concept of Karma should be implemented in the Fediverse. At least not, like we know it from Reddit.
Reddit's Karma was handled like a currency, and in order to obtain such, the overall-quality of the content declined as a result of Karma-farming.
In my opinion, the fediverse feels so new, fresh and exciting, because there is no such thing as Karma. No barrier that hinders one to post someting, because a certian count of Karma - or Lemmy-Schmeckle, call it as you want - would be needed to post something. Yet.