I was very careful not to mention blogs specifically. All sorts of content stimulates emotional responses and thus comment - photos, comics, software, articles,

I was very careful not to mention blogs specifically. All sorts of content stimulates emotional responses and thus comment - photos, comics, software, articles, and yes, blog posts. As a feedback mechanism the "blog format" is de rigueur. Fifteen years ago you would have sent an email. Disagree that Tipjoy doesn't add value to Disqus simply because comments are so often a statement of appreciation - local customs aside, that's what a tip is too. Appreciation of the value provisioned, if you prefer. What you get is distribution channel for Tipjoy and a product enhancement and revenue slice for Disqus. Another aside: Tipping of high value comments would be possible. There are plenty of times the OP has been light on value but the comment stream is a gem - we see it on HN all the time.