Deep down inside he's probably scared that Stackoverflow users also roam Hacker News & the Internet at large and doesn't want his blog post to become a honeypot for scorn. Honestly, I understand completely where he's coming from. I've posted answers to SO and received lots of "well that's obviously wrong" kind of comments - it took me months to realize what was so wrong about those answers (why couldn't they just tell me). The SO crowd can be extremely purist & hostile. But I suppose that's what drives quality in their answers.