I am amused by the site being down. Going back to WordPress, he presumably forgot that a cache plugin is pretty much required. Not that Jekyll is perfect, but that's one area where it's pretty much impossible to beat.
Wordpress cacheing HN traffic should do fine too. There's something else going on here.
HN traffic isn't really that much. I was watching the stats under the new Google Analytics realtime mode and the site was averaging about 3 - 6 requests per second.