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!