We didn't shadowban them, we told them we were banning them: https://news.ycombinator.com/item?id=34916347, we told them why, and it wasn't the reason you've presumed.

When people presume things about moderation, they almost always get it wrong. That's a pity because all anyone has to do to get the correct answer is ask us.

If you see an account that's banned and you don't think it should be, please let us know at hn@ycombinator.com so we can take a look. We've unbanned quite a few accounts that way. In the meantime, you can vouch for their good comments (see https://news.ycombinator.com/newsfaq.html#cvouch). But please don't divert the thread with offtopic noise that is likely to be incorrect.

For that one comment, probably not, but maybe for dozens of previous flagged and/or dead comments

Once you're shadowbanned your comments start off as dead by default and have to be vouched to be visible.

Ah, I wasn't aware of that--thank you for the clarification.

looking at his (recent) comment history, I can’t imagine this is the one in particular that got him shadow banned.