Every time I've looked into it, when you see suddenly and without reason ban-banned after a string of real comments, the backstory has been that it's someone with a track record under other usernames.
At some point, no matter what HN does, being comfortable with its moderation requires you to take Dan's word for things. I take his word for it on shadowbans.
Ironically, I'm irritated with moderation in the other direction: ten years of "if you keep breaking the guidelines under alternate accounts, we'll ban your real account" sort of makes my blood boil (people having long-running alts does that too), but I roll with it, because I couldn't do the job better than Dan and Tom do.
>the backstory has been that it's someone with a track record under other usernames.
This has gaps, as you know, and doesn't wash. Let someone turn a new leaf. Amnesty puts a stop to this.
I don't think it does, no. I've seen people raise innuendo about this kind of thing for over 10 years and have never seen someone vindicated. Maybe you have an example you can share.