A List of Hacker News's Undocumented Features and Behaviors
Hacker News, a simple link aggregator owned and operated by Silicon Valley startup incubator Y Combinator, has had many positive effects on SV startups and engineers as a whole. On Hacker News, users receive Karma whenever another user upvotes a submission or comment they made, which incentives positive contributions to the community.
However, in maintaining its simplicity, many new features and behaviors added over the years on Hacker News are not fully documented other than the occasional comments from staff. This list details some of the hidden norms about Hacker News not otherwise covered in the Guidelines and the FAQ, along with a few bonus features outside of typical HN usage. If there is anything missing/incorrect from this list, feel free to file a GitHub issue/PR.
This list has no affiliation with Hacker News, Y Combinator, or any YC-backed company.
Hacker News currently has one full time moderator: Dan Gackle (dang), and formerly Scott Bell (sctb). Their commentreplies provide a pseudo-log of Hacker News moderation.
Dan is very responsive when contacted at email@example.com, and is the best option for resolving any issues on Hacker News.
All comments start with a score of 1 point (but in order to prevent bandwagoning, the comment score is not visible to users other than the author). After users reach 501 Karma, they gain the ability to downvote another comment. Downvoted comments (i.e. with a score < 1) reduce their placement on the comment thread and will appear desaturated to other users deemphasize them. There is no upper limit on the score of a comment, but the minimum score is -4 points. You cannot downvote comments which are direct replies to your own comment, and you cannot downvote 24 hours after the original comment was made.
If a user has 31 Karma, they can flag submissions. Although submissions cannot be downvoted, flags act as a "super" downvote and enough flags will strongly reduce the rank of the submission, or kill it entirely (flagging is supposed to be used for submissions which break the site guidelines, but that isn't always the case in practice). A submission that's flagged to death will have a [flagged] tag. Comments behave similarly.
A [dead] submission (that does not also show [flagged]) is killed by a moderator or by the software. They will only be shown to users who have showdead enabled in their profile. A submission can simultaneously be [flagged] and [dead].
If a user has 31 Karma, they can also vouch for a [dead] submission/comment. A vouched submission/comment has its rank restored (and potentially improved as the vouch can counteract the effects of flags), but it can be [dead] again at which point it can't be re-vouched.
Setting Top Color
If a user has 251 Karma, they can set the color of the top bar in their profile settings. The default is #ff6600. Here's the complete set of colors users have set.
The FAQ states "users should vote for a story because they personally find it intellectually interesting, not because someone has content to promote." Indeed, Hacker News utilizes a voting ring detector which will prevent caught submissions from hitting the front page. Due to sites like Product Hunt normalizing the asking for upvotes or other engagement via social media, the implicit asking of upvotes is also done for Hacker News, usually due to ignorance of the Hacker News rule against it. There are very few good reasons to draw attention to a Hacker News submission immediately after it has been submitted.
One popular "trick" for obfuscating voting manipulation on Hacker News is to link to the Hacker News's /newest page of new submissions (instead of a direct link which would otherwise make voting manipulation obvious), and asking friends to upvote the submission from that page. This trick doesn't actually work.
The FAQ notes that submission rank is impacted by "software which downweights overheated discussions." A good rule of thumb for this effect is when the number of comments on a submission exceeds its score. Moderators can overrule the downranking for appropriate, not-actually-a-flame-war discussions.
Moderators will sometimes rescue a post which didn't receive a lot of upvotes and reset the submission time on the post. (This is also one of the reasons why the FAQ discourages deleting submissions).
Relatedly, moderators can also invite users via email to resubmit a post which didn't get much traction.
Edit/Delete Time Limits
After a post or comment is made, it can be edited by the author within 2 hours. A post/comment can be deleted by the author within those two hours, but only if it has no replies, in order to prevent discussion from being lost. In that case, the post/comment cannot be deleted (This can result in a fake [deleted] edit if a person wants to remove their comment in the limit but can't).
Moderators can change the title of a submission at any time.
Comments can be collapsed by clicking the [+] icon to improve readability.[flagged] comments are sometimes collapsed by default, and moderators can set a comment to automatically be collapsed if necessary (e.g. meta-discussion).
When a comment thread is collapsed, the [+x] number on the right indicates the total number of hidden children comments.
Both users and domains can be shadowbanned, where all posts/comments by that user / submissions to that domain will be instantly [dead] and cannot receive votes/comments (but can still be vouched). For accounts with a substantial history on Hacker News, moderators will give warnings before a ban.
A good way to tell if a user/domain is banned is to either have another user with showdead enabled check for a series of [dead] content from that source, or view those submissions in Private Browsing/Incognito mode to see if they appear.
Accounts which are less than 2 weeks old will appear with a green username.
Thin Black Bar
Occasionally, there will be a thin black bar at the top of the top bar, in memoriam of a significant figure in the tech/science community dying. A Hacker News submission about the death will usually be at the top of the front page at that time.
Implicit Downranking of Politics
The Guidelines state that most political discussion is probably off-topic. However, the line between technology and politics is blurred, especially as of recently. Most tech related submissions with a hint of political partisanship will quickly be flagged to death by users (or die a slow death due to the inevitable flame war).
Implicit Downranking of Topics Around Diversity and Inclusion
Likewise, topics around diversity and inclusion in tech have gained lots of visibility over the past few years. However, despite these discussions not being off-topic, they tend to be flagged to death by users regardless. Unfortunately. (Moderators occasionally unkill such threads if they see it in time, although it rarely sticks).
Many news websites have started implementing a paywall for their content, which has caused conflict with Hacker News's "original source" rule. The web button next to submissions (that does a Google search for the given title) was partially intended to serve as a paywall workaround; however, recent changes to the paywall implementations have closed that loophole.
As a result, submissions which link to paywalled sites tend to get many comments complaining about paywalls, which are off-topic.
Perceived Favoritism Toward YC Companies
YC Companies get two notable benefits on Hacker News; they can post jobs ads to the front page (which start off at Rank #6, cannot be voted/commented on, and have a fixed decay rate), and the ability to do a Launch HN when their startup launches out of a YC batch.
Currently, there is no evidence that non-job submissions about a YC startup receive preferential treatment on the front page, or kill submissions critical of a YC startup. In fact, the moderators have stated that they explicitly avoid killing controversial YC posts when possible.
Additionally, founders of YC companies see each other's usernames show up in orange, which — although not an explicit benefit — does allow fellow YC founders to immediately identify one another in discussions.
Hacker News allows users to see what the front page looks like at any point in time. You can also do a wayback view for any user at their registration date by clicking their registration date in their profile.
Hacker News on BigQuery
If you want to gather large amount of Hacker News data for data analysis/machine learning, you should use the Hacker News dataset on BigQuery, which is updated daily and is much more pragmatic to use than manually scraping data from the Hacker News API.
Hacker News Lists
Hacker News maintains a list of useful links that allow for primitive filtering by certain types of content. These currently include:
/leaders — View a list of users with the most karma
/front — Filter front page submissions for a given day (e.g. 2016-06-20), ordered by time spent there