Reddit - Greyscale - No Karma
This userstyle is derived from "Reddit - Hide All Karma" by Reddit user gavin19. (However, I have his blessing to put it up on here.) It completely removes all instances of karma from the Reddit website. If you want the greyscale theme to work consistently across all subreddits, you must uncheck "allow subreddits to show me custom themes" in preferences > display options.