I once ran the numbers for HN and was surprised at how closely they matched this rule. Maybe I'll do it again. Edit: here are some estimates. We don't track enough to know about distinct users, so all we can do is guess. The number of accounts that have posted to HN this year, divided by the number of IP addresses that have accessed HN, is 0.008. How close that is to the '1% rule' depends on which is the bigger facto…
I used to submit more years ago, but it got ridiculous to get votes. I suspect there must be a LOT of brigading to get posts out of the /newest cesspool.
It's of course possible that some people are clever enough that we don't even know what they're getting away with. But I can tell you that HN's anti-voting-ring software catches a great many cases. So many, in fact, that we'll often go through that list and remove the penalty on particularly good submissions, because sometimes people were clueless about trying to promote otherwise good content.
Edit: the other thing is that we regularly get independent confirmations that the anti-voting-ring software works...so at least it's not totally off.