Given how much content gets pasted here from /r/programming and other tech subreddits, and how much passion there is behind HN's distaste for the redesign, I would bet that many, if not most, HN users are redditors.
Those are a weird minority of subreddits. Look at the front page for a taste of how Reddit is experienced on average.
Still bit away I'd say tho, reddit commenting style leaks out in some topics