My posts are never "shadow deleted" they in fact sometimes get a boost from the mods when they though it just missed the mark timing-wise (i.e. interesting post, but some breaking news thing happened, and I didn't get the love).
The moderators only car about keeping the discord civil (as civil as possible), and the posts relevant/interesting for their niche.
There probably is a "club" - but not being in it doesn't get your content shadow deleted. It just wasn't interesting enough at the time to get votes.
I mean, this post isn't really big news, it feels like it's just barely scraping by the notability/interest level required to make it on HN. Mostly, I just think the presence of some kind of cabal or conspiracy is a lot less likely than "mods are human and thus subjective and inconsistent".
But you can always email the mods. They're very responsive.