In the situation of jury nullification, though, the judge would have to be punishing a juror for the verdict they supported. That isn't legal at least in the US, a juror can't be instructed to give a certain verdict or punished based on their decision.

Judges will be careful not to directly give instructions against nullification for precisely that reason. They may very well imply that you shouldn't go off the rails of evidence provided or laws and precedent as described, but that's as far as a judge can go with instructions against nullification.