So, I always browse Hacker News using "showdead" (and have since I started using the site): there are definitely ghosts walking among us that have no clue they have been hell-banned; to be clear: "people are submitting stuff, not realising that it'll never be read".
Yes: a lot of the time, when a comment is marked "[dead]", it makes sense that that comment is dead. However, you cannot use this to determine whether the instances of hell-banning are appropriate, as most comments that are marked "[dead]" are not dead because they were posted by someone who is hell-banned: that one single comment is dead.
Sometimes, though, a comment is actually useful (occasionally even, the most useful response), and you wonder "why is this dead?": the result of seeing someone who has spent the last few months talking to the small handful of people who care enough to use "showdead", not ever realizing it or being told it, is kind of sickening.
At some point, I decided to start leaving tabs open with these people (my really pathetic way of bookmarking stuff), so I could one day find them all and write an article about "why you have to be careful when you implement hell-banning", but unfortunately (as this is a really pathetic way of bookmarking things), I can't find some of my better examples, despite spending the last two hours searching through current and archived browser states.
However, I do have at least one example for you: this comment has a response from a user named "Pooter" that I found interesting--in fact, multiple people found interesting (enough that someone actually asked after it)--and yet the user is hell-banned, so I don't get to see it. This user is /still/ posting stuff, and probably /still/ doesn't realize they are hell-banned.
http://news.ycombinator.com/item?id=2519863
Now, when you look at this user's comment history, it is not at all clear to me that he deserves to be /hell-banned/. Yes: some of the things he says are not terribly useful, but if you check the threads there are other users who say the same things and are simply slightly downvoted; in some other cases these alternative comments are standing fine.
But what is really bothersome is that sometime this is the only user who went out of the way to correct someone else, and Pooter is actually right:
http://news.ycombinator.com/item?id=2872773 <- in fact, iOS has support div scrolling for years, maybe even since the beginning: Pooter is right
http://news.ycombinator.com/item?id=2846808 <- while I'm not certain who I agree with there, I think Pooter's argument is a reasonable one, especially if you connect it with his other rebuttle: http://news.ycombinator.com/item?id=2843802
http://news.ycombinator.com/item?id=2808094 <- this comment is downright insightful: I am fully in agreement with it, and I wish I had been there to say it.
http://news.ycombinator.com/item?id=2755767 <- while he didn't need to say "This is a stupid idea.", his reasoning for why the idea is not "very good" is sound.
When I come across these cases, it really makes me wonder what is going through the minds of the people who are making these moderation decisions. I mean: Pooter is abrasive, but I've spent a bunch of time over the last few days staring at HN users (and tagging them: I got sick of not remembering who is who, so I've built a user tagging framework), and there are people with many thousands of karma points who cause a lot more strife with a lot less useful content than Pooter (or the other people I swear I have sitting in tabs somewhere on one of these numerous web browsers :().