It kinda sucks that the name of this concept (shadow ban) is completely ruined by analphabetic luddites (hyperbole, don't worry) calling every platform that ignores them a bunch of shadowbanners while it might simply be a case of an eventually consistent database, a hype algorithm that chose someone else's message, or a feed curation mechanism that simply doesn't include everyone else's messages.
A more usable term might be 'muted' or 'hidden' instead of a complete 'ban without letting you know'. Internally it's even more likely that they work with an extra reputation system next to the visible karma system where new accounts are simply given 'bad' reputation way sooner than they should. Considering mod-communication works fine, it's probably just shoddy spam protection systems combined with a recursive problem of not having enough reputation to post, which is required to gain said reputation.
A more usable term might be 'muted' or 'hidden' instead of a complete 'ban without letting you know'. Internally it's even more likely that they work with an extra reputation system next to the visible karma system where new accounts are simply given 'bad' reputation way sooner than they should. Considering mod-communication works fine, it's probably just shoddy spam protection systems combined with a recursive problem of not having enough reputation to post, which is required to gain said reputation.