I don't like that it's just as much of a time hole as any social media and 99% of the content isn't actually relevant to my life, but I might read it anyway knowing full well I'm wasting time.
There will be a long really in depth article about a topic and then the discussion in the comments will be about something totally irrelevant to the article, like the font/formatting of the article/website
Dislike: Down voting. Down voting just makes for an echo chamber (as someone else already mentioned.) It's a terrible, nasty, way of punishing people who's posts don't fit the popular cliques viewpoints. It should be replaced with either a mandatory "this is why I down voted" comment, or flags that everyone can see. Like "off topic", "insulting", "spam", or things like that. At the least, it should cost karma to down vote. Oh, and if you down vote, or flag, and it gets reversed, you should lose karma.
That's one of the main things I don't like about reddit
HN loads fast and has next to no ads.
Dislikes: sometimes overwhelming pedantry, and recurrent culture war garbage masquerading as Libertarianism.
Inability to delete your account.
I don't like downvotes (in part because it makes upvoting difficult on mobile), and would prefer a flag-for-review (to further tax the mods, I assume), but if the fade-out from downvotes helps reduce spam and low-quality responses, I can live with that.
I also don't like that there's a dopamine drip of upvotes at all, and find the number near my username distracting. This is the only social media platform I use, and most of the time I'd rather be reading a book but this is so easy to browse.
Posts like this are a helpful kick in the pants to go away and read a book.