Not sure if you strictly mean karma per submission, or karma per comment, or both. As for karma per comment at least, reaching a critical mass of absolute karm

Not sure if you strictly mean karma per submission, or karma per comment, or both. As for karma per comment at least, reaching a critical mass of absolute karma points seems to have a big impact on your KPC, regardless of the comment's content, thus partly invalidating the value of KPS/KPC. I just anecdotally see karma peasants post comments that are functionally identical to comments from the karma kings, and the peasants just get buried at the bottom. It would interesting to have some kind of NLP-based crawler go through HN and see to what extent that actually happens though...maybe it's just my imagination.