This is a really useful list, thanks for putting this together.
I was briefly shadow-banned a month or two ago, due to a few submissions of posts on my personal blog from this account (and not much else).
What was odd was that when I looked at the "newest" page while logged in, I saw my post on HN but when I looked when not logged in, the post didn't show up. I didn't know shadowbanning existed and thought there was some kind of issue with HN, so I emailed hn@ycombinator.com. dang@ sent back an incredibly thorough and thoughtful reply literally 3 minutes later (this was at 7:15 p.m. on a week night).
So while I find it a little odd to 1) shadowban someone without telling them why and 2) intentionally obfuscate the fact that they've been banned by making it seem to them like their submission was successfully submitted, I was really amazed by the care and efficiency of dang's response. So thanks dang!
If you were a low-effort spammer (Edit: I'm not suggesting you are a spammer btw) you'd never notice and keep on posting spam into the void. Whereas if you were notified you might create new accounts ad infinitum increasing the administrative burden of HN.
I once implemented a similar feature for the comments on my blog along with an embarassingly simple filter to identify the spammers initially. The volume of spam on a no-name nerd's blog and the degree to which this approach resolved it were both surprising to me.
On a later incarnation of the blog I just removed the commenting feature, but I guess that wouldn't be a sensible strategy for HN :)
The entire point of shadowbanning is making the fact that the user is banned non-obvious to that user--otherwise, they'd be liable to immediately create a new account and continue with the activity that warranted the ban in the first place.
Both "telling them why" and "not obfuscating the fact" would defeat the entire purpose of a shadowban (as opposed to a "traditional" ban).
The whole point of shadowbanning is that the spammer/annoying poster doesn't know they're banned and need to create a new account to keep trying to spam/troll the board. If you tell them generally they'll just create a new account, it's especially bad for sites like HN where there's not even an email required for creating an account. As it's gotten easier to create temporary emails shadowbanning becomes increasingly more effective because it increases the amount of spam that gets blocked before the account owner notices to create a new one.
Meanwhile million dollar corporations buy accounts and astroturf with no penalty.
The little guy is silenced from sharing opinions/links that God Mods don't like, but the big corp can write off a marketing expense that looks like a mature organic account to God Mods.
You have no evidence of that, and neither do we (right now).
When we do get evidence of that, we crack down hard. We've done that in the past in two different $BigCo cases—but this is very rare. What's not rare is internet users making up stories about it based on their feelings. That's so common that the site guidelines ask HN users not to do it: https://news.ycombinator.com/newsguidelines.html.
We unban accounts when they give us reason to believe that they'll follow the site guidelines in the future. You could start by following the site guideline which asks you to email such questions to hn@ycombinator.com rather than posting them to the threads. If your recent comment history looks good (spoiler: it mostly does), we'll be happy to oblige.
I was briefly shadow-banned a month or two ago, due to a few submissions of posts on my personal blog from this account (and not much else).
What was odd was that when I looked at the "newest" page while logged in, I saw my post on HN but when I looked when not logged in, the post didn't show up. I didn't know shadowbanning existed and thought there was some kind of issue with HN, so I emailed hn@ycombinator.com. dang@ sent back an incredibly thorough and thoughtful reply literally 3 minutes later (this was at 7:15 p.m. on a week night).
So while I find it a little odd to 1) shadowban someone without telling them why and 2) intentionally obfuscate the fact that they've been banned by making it seem to them like their submission was successfully submitted, I was really amazed by the care and efficiency of dang's response. So thanks dang!