They're kind of caught between a rock and a hard place here.

HN doesn't have a lot of resources to combat abuse (notice how much abuse prevention is just 'dang --- who runs all of HN --- personally writing corrective notices [they're not even the same notices! Dan, get a shortcut completer!]).

I think a pretty big part of their strategy is to wait for serial abusers to do something stupid and then penalize their accounts. It's an arms race. If they list all the things you can do to get a submission penalized, they're making it harder to catch serious abusers.