Earlier quoted context omitted.
I know that as shadowbanning. This is one of my favourite reddit posts on the subject: https://www.reddit.com/r/tifu/comments/351buo/tifu_by_postin...
IIRC hellbanning is a variant of shadowbanning that prevents easy discovery of the banned status by putting all suspect accounts into the same "hell" invisible to normal users. This works well if you have a network of fake accounts from a single "persona" or ring of personas - by all their indications they can't see their own posts are being ignored. Notice: it's almost the exact response to the persona management so…
Neither reddit nor HN make any attempts to make it hard for sophisticated users to figure out they're shadowbanned.