OK. Here are just three I spot at the moment from the first 2 or 3 pages I see, when browsing the site by the /new sorting:
1: [dead] Protect your S3 buckets from breaches (mklein.io) [0]
2: [dead] The NSA just released the preview version of Ghidra Debugger on GitHub (github.com/nationalsecurityagency) [1]
3: [dead] How to Write a Terminal Multiplexer with Rust, Async, and Actors – Part 2 (hashnode.dev) [2]
I'm not saying any of those is a fantastic article, or one that particularly interests me. But I can't see anything particularly 'wrong' with them in an abusive, spammy or 'irrelevant to HN's readership' sense. And, as I said before, there are usually at least one or two such submissions, which seem to have been killed for no apparent reason, on every page when browsing by '/new'.
Interesting you should say there's more complicated filtering going on behind the scenes because, from this side of the wizard's curtain, it does often look arbitrary, almost like people are flagging stories for personal reasons other than completely objective ones. And, as I said previously, one of the reasons I had turned 'showdead' on.
[0] https://mklein.io/2020/12/17/protect-against-s3-breaches/
[1] https://github.com/NationalSecurityAgency/ghidra/tree/debugg...
[2] https://github.com/NationalSecurityAgency/ghidra/tree/debugg...