You need to have enough karma to do so. I'm not able to downvote as well. By engaging and adding value to the discussions posted you will hopefully be able to have this and other features unlocked.
It’s not everything it’s cracked up to be. I hardly ever use it. In principle, downvotes are meant for messages that are irrelevant, off topic, insulting, belligerent (can you believe my phone turned that into beliebers?) etc. The effect stops at -1 or -2 points, I believe, so it’s quite likely that a really upsetting comment has already been downvoted maximally. And you can’t downvote replies to your own comments, nor submissions. Not worth losing any sleep over.
Perhaps it is a good thing that you can't downvote. I'm not sure. Is being able to downvote a necessary condition to "engage"? Or does not being able to downvote force us to engage, not with an easy click, but with a considered comment?<p>Perhaps this condition adds to HN's value as a venue where you can expect to encounter thoughtfulness? It's why we come here after all. Or perhaps it trains the new user how to use the site in ways best suited to HN's culture?
Is it really such a useful feature, though? I have mixed feelings about the way this is used on StackOverflow, for example. I post there extremely rarely and it always bugs me to get a quick downvote without any explanation or anything. I'd very much rather see my post get no or very few upvotes and maybe some constructive comments on how to improve it than to have people use the lazy one-click solution to downvote it into oblivion.
You can find the details here: <a href="https://github.com/minimaxir/hacker-news-undocumented#downvoting-comments" rel="nofollow">https://github.com/minimaxir/hacker-news-undocumented#downvo...</a>
I've got >500 karma. Why can't I downvote certain users or comments, reply to certain comments, and occasionally appear to partially lose the ability to downvote for a period if comments I post receive downvotes?
It’s based on how much karma you have. The more you engage the more features are unlocked.<p>Personally, I think flagging should require 5000+ karma, not sure what it is.<p>I think up and downvotes are >500 karma