Have you considered, perhaps, changing your behavior?
If you're concerned about a specific IP, and haven't been abusing HN, it should be easy to clear up by emailing hn@ycombinator.com. And even if you have been abusing HN, we're always happy to unban people (and/or their IPs) if they give us reason to believe that they've taken https://news.ycombinator.com/newsguidelines.html to heart and will follow the rules in the future.
Edit to add: Without more details from you, I can imagine the mods being hamstrung with respect to figuring out or explaining what's going with what you're observing. Likewise, there's nothing preventing you from continuing your comments here while also emailing them. Particularly as it seems you'd like to continue to participate on HN. I can imagine you'd prefer to do so without the hassle you're currently experiencing.
Perhaps that is done to avoid the rate limiter?
I can usually only make five posts in one 8-hour span, and then the sixth attempt says, "You're posting too fast. Please slow down. Thanks. Also, don't count the number of posts tptacek can make in one thread in one hour and compare it to your total for the entire week, or it might raise your blood pressure."
I am barred from having more than half a conversation in one day, while it seems that [some] others can post as often as they can hit "[reply]". So yes, I do feel censored on HN. The article didn't even mention the post-rate limits.
Also since you mentioned a particular user your comment will be removed. Funny how that works.
I can recall at least one instance where he replied to me directly, and I wanted to engage, but couldn't, because I was "posting too fast".
It's the network neutrality issue writ small. Some people have fast lanes on this site, and others have slow lanes. I don't like it here, and it annoys me when I notice it. If it becomes the status quo for the whole network, you can be sure that I will be engaging in "shovel vigilantism" in the dark of some nights. Freedoms of speech and publication are no longer supportive of liberty and equality when certain favored people are allocated 10000 times as much speech as most other people are usually allowed, and drown out all other voices with their sheer volume rather than the merit of their claims.
At some point I noticed that I never got replies, but didn't think much of it, continued posting. Then, one day I looked at my profile while I was logged out, and surprise - the the posts for the last few months are no longer there.
Like OP, I went through a few accounts. They worked for a bit, and then responses dropped off. Eventually, I realized that apparently, my new apartment's IP is toxic.
Not sure who a shadow ban is supposed to punish since any spam bot can check just as trivially of they're banned. On the other hand, legitimate users have no idea keep wasting their time submitting their comments to /dev/null.
By now I have given up on trying to comment on HN. I can use my time on better things.
Ironic that a the site like HN can't get a proper quoting markup, can't fix the pre-block scroll, took forever to add support for mobile and comment collapsing, and used blanket IP bans...
Shadowbans are reversible by users and can be appealed to the mods, assuming you notice it (which, by design, you're not supposed to.) This is supposed to ensure that only accounts which should be banned remained banned.
It's not perfect, but it does make sense - the only real options for banning are by IP and by account, so if you want to prevent a banned user from just making a new account, you have to ban the IP as well. Maybe someone was a troll and got that IP banned, maybe it appears on a blacklist (assuming HN checks that,) who knows? It's not random and arbitrary, though.
Maybe that is the problem.
Why are you so surprised he might have multiple accounts? You really have one email account? How about work-related email? Company-facing related email? If anything, its actually good he has multiple accounts and stuff related to / from his company account he is posting from company, and private is private.
No, I have 5, but I only have one HN account. Why would I need more?
I was thinking more that he might have been identified as being the same person posting from multiple accounts, and activating some kind of spam/abuse protection.
For same reason you have multiple email addresses no?
Others might but I can't think why off the top of my head. The only time I've seen an obvious alternate account is the throw-away accounts opened just to troll/spam the site.