As someone who has looked into this area for Reddit and HN data, here are a few additional notes before everyone starts submitting their blog posts and marketing pieces to HN on weekday mornings:
1) After everything, the analysis is probabilistic. You are not guaranteed to get onto the front page just by submitting on at a high-probability time.
2) There are game-theoric implications; the more people submitting at a time (weekday mornings), the less likely people will see your post on /new before it is pushed off the first page, and it is highly unlikely to get upvotes once it has fallen off the top 30 slots. (hence the repost/second chance rules)
3) For obvious reasons, don't submit if there is important news occuring. (e.g. Apple/Google/Microsoft event)
4) Above all, if your submission does not get any upvotes, don't interpret it as your post being low quality. The median score of all submissions is 1-2 points regardless of time submitted. (http://i.imgur.com/SN5BuAJ.png)
The OP is impressively throrough regardless, especially since working with ranking data-over-time is much better than working with raw data.
To paraphrase the original article that inspired the OP, the Hacker News front page is not a meritocracy. There are optimizations that make your submission more likely to be upvoted (a simple one being a clickbait title). It is worth noting that this submission would have different behavior with the original title "You only need 3 votes to play, and other facts about the Hacker News frontpage." (and apparently it was just changed to that, and penalized?)
That's also why a good moderation team is necessary and important; to fix submissions which are not inherently good, and to boost submissions which are not inherently bad.
Also, your post will get weighted down if it contains certain words or is from a certain domain. I believe at one point 'NSA' got you penalised (due to the high number of NSA links coming in at one point in time), and Medium posts have a tougher time getting onto the front page (due to the lower signal:noise ratio I guess).
There's more than a bit of leftist elitism at work. E.g. I once made the mistake of submitting something from breitbart.com. It never appeared in 'new'.
When I'm logged in, it shows me that I've submitted 5 items. Examining my submissions anonymously only shows 4 items. Perhaps there are 5 if someone has 'showdead' on?
Putin's external propaganda site, rt.com, is OK, heaven forbid that Breitbart be afforded that same privilege.
I think the simpler reason is for a similar reasons as to why Medium get's penalised by the algo - links from Breitbart (and Medium) generate less useful discussions than other sites, thus they must 'work harder' to 'earn' their place on the front page.
Similar to the 'flame war detection' that flags posts with more comments than (up)votes.
NSA got me penalized from 2013 onward if I said anything positive about them on about any security or IT forum. Evidence or accuracy didn't matter due to polarization. So, this is more true than you say. Less now but the effect is still there.
Also I think there is something to be said about the comments section of the post. I rarely up vote anything, and if I do it's usually an afterthought after I've read a good discussion in the comments. I've also caught myself on multiple occasions up-voting a submission after I made a comment on it, simply so that my comment would become more visible and be up-voted.
I think there are a lot of intricacies involved in these systems, and that they can be gamed for personal gain, ala much of reddit.
I frequently upvote submissions that have good comments, even if the article is not-so-good. There really should be two different upvotes, one for submissions the other for comments.
1) After everything, the analysis is probabilistic. You are not guaranteed to get onto the front page just by submitting on at a high-probability time.
2) There are game-theoric implications; the more people submitting at a time (weekday mornings), the less likely people will see your post on /new before it is pushed off the first page, and it is highly unlikely to get upvotes once it has fallen off the top 30 slots. (hence the repost/second chance rules)
3) For obvious reasons, don't submit if there is important news occuring. (e.g. Apple/Google/Microsoft event)
4) Above all, if your submission does not get any upvotes, don't interpret it as your post being low quality. The median score of all submissions is 1-2 points regardless of time submitted. (http://i.imgur.com/SN5BuAJ.png)
The OP is impressively throrough regardless, especially since working with ranking data-over-time is much better than working with raw data.