This works well if you have a network of fake accounts from a single "persona" or ring of personas - by all their indications they can't see their own posts are being ignored.
Notice: it's almost the exact response to the persona management software problem  (aka bots).
Give them their own queue with their own games with other cheaters to play against, and as long as nobody is cheating in a way that breaks the servers, they can play their own version of the game if they want without ruining the game for those who don't cheat.
Neither reddit nor HN make any attempts to make it hard for sophisticated users to figure out they're shadowbanned.
Of course your main point - that this is all terribly imperfect and won't stop a determined, sophisticated user, who has realized what's happening - is spot on. That, however, is perhaps a rare combination, rare enough to simply continue dealing with manually.
IA was just an example, and Tor would be easier. But anyway, I think it shows the flaw in doing so:
> You could also shadowban IA.
If the spammer manages to get all the IPs hellbanned just by looking at things, he gets more eyeballs on his spam.
My point is, you can't get much better than normal shadowbans, which are trivially detectable for moderately sophisticated users (just log out and try to check your profile) but not anyone else. "Hellbanning" is a stupid extension of this concept which only works in video games.
Also, shadowbanning is a spineless and deeply unethical move. If I get banned, I know what I did wrong and can reflect on that. If I get shadowbanned, I'm just screaming into the ether. That is not a Good Thing™, it is atrocious.
Depends on the use case. Once every 24 hours is a lot easier to moderate than a minute by minute spam wave.
> IA was just an example, and Tor would be easier.
TOR would indeed be easier... assuming it's not already blocked through other means, as it frequently is. There's a whole ecosystem around blocking TOR and other proxy mechanisms - imperfect and permeable though they may be.
> My point is, you can't get much better than normal shadowbans
Not sure I agree or that you've supported your point - however, even shadowbans are often unnecessary. The goal is never perfect moderation, merely to stack the deck in favor of the moderators for blocking problematic content in terms of time effectiveness until either the moderation effort available can handle it, or until the spammer moves onto easier, more cost effective targets (which even basic shadowbanning can achieve, mooting the need for better tools even if they're available.)
> Also, shadowbanning is a spineless and deeply unethical move.
As a first line of defense against mere rules breakers, I might agree. As a second, third, or nth line of defense against particularly problematic ban evaders and spambots, I will gladly resort to such tools - or worse - and sleep soundly at night.
So then you will have no problem recognizing where I'm coming from when I say that the Hacker News 'mods' are some of the most evil Nazis on the planet. After all, I created my first account here only a few months ago, and was shadowbanned in less than 15 posts despite posting with honest intentions. Is that what decent people do to other people?