What are some reasons a Show HN post might get flagged?

Question

When I browse https://news.ycombinator.com/shownew with showdead on, I see several posts flagged into the oblivion. None of them strike me as obviously egregious and I'm curious how they ended up this way. I can understand flagging of obvious spam / undesirable content on the "new" page, but Show HN is where folks show off what they've built. Would love some perspective on motivations behind flagging those messages.Full disclosure, I did my first Show HN earlier today (something I worked on on my own for a while) and though it got some votes, apparently it also got flagged and while not dead, this prevented it from ever surfacing on the "show" page. Life goes on, but it really piqued my curiosity!

mtmail · Accepted Answer

Those [dead] are not flagged (it would show [flagged]), it's algorithmic. Usually brand new accounts where another old account will need to click 'vouch'. There sometimes aren't enough users browsing the /new queue. Especially all the github repositories became boring to me, for example code that was pushed to github only 5 minutes earlier with no documentation. 'Show HN' is the most misunderstood label and some users use it for blog posts or websites they didn't work on (like a wikipedia).
I remember your website and see it in my browser history so I most likely clicked 'vouch' (browser history doesn't tell).
It has 8 upvotes and not listed on /show. That's usually a sign that friends upvoted. By that I mean accounts who visit hackernews, upvote and then leave again. I'm not saying that happened here, I've just seen this algorithmic behavior in the past, for example I checked twitter and the author posted an 'upvote my submission on $url'. Apparently that's normal for producthunt but discouraged on hackernews. I have no insight into the actual algorithms.

gsuuon · Answer

It looks like all the current [dead] links violate the "Please don't use HN primarily for promotion" guideline.