Reddit shows up/down totals on users, comments, and stories. It's really in your face. HN has a subtle little arrow or two, and you only see the sum of up/down on your own comments. We know when things have been downvoted, but it's much harder to tell if something has been upvoted. And when things do get downvoted, they're grayed out -- it takes more effort to read downvoted comments (click the date), so if you're skimming you'll just skip unpopular comments until it gets relevant again. So display-wise, I like the cleaner HN over the noisier and visibly gamified Reddit.

Also, not insignificantly, HN is a side project, not a startup. It can succeed at its goals and stay small, not worrying about "capturing the market" or whatever. Staying small means dang can generally be expected to read most of the comments on the site.

And by "small", I mean that there's rarely much action on the page-3 stories. Threads that get paginated are rarely worth wading into. If a million people started using HN, then it would quickly become so unusable that they'd all quit within a week. Reddit "solves" this "problem" by making subreddits, and now it's a poison-breathing hydra.