Honestly I had no interest in anything associated with Kevin Rose thanks to Digg.
Slashdot had moderation for comments, but no similar mechanism for stories. Digg had the voting system for stories and for comments.
I don't know the Reddit history that well, but as I read recently in a PG essay, it was originally slated to be a food ordering application on your phone.
I do not know when they pivoted, or when their idea to pivot came, but I _suspect_ that their pivot was at least partly inspired by Digg's early release.