Now that I've read further comments in this thread, I now know that rate limiting is manually applied per account, something that afaik has never been explicitly acknowledged before, and is certainly not acknowledged in the deceitful (at least partially) error message: "You're posting too fast".
It's interesting how human judgement of how appropriate/ethical rules and procedures are is often altered by whether or not one is part of the ingroup. In a generic conversation, say on software design principles, I suspect most people would certainly say that objective honesty/correctness is something to strive for, but when the conversation is in this particular implementation, I bet opinions would change.
Another interesting related issue, something one might notice that isn't in the HN guidelines: "Try to be honest; try to speak truthfully." I've suggested this before, but apparently it wasn't deemed important enough, which seems like quite a shame to me because it has become quite a common behavior on HN.
Of course, these things aren't surprising, but they are interesting.