It's essentially a threaded HTML-box overlay for a certain part of text. I think that's how you would implement such a system, isn't it? Just because RG uses it

It's essentially a threaded HTML-box overlay for a certain part of text. I think that's how you would implement such a system, isn't it? Just because RG uses it for explanations doesn't mean that it can't be used for exposition/comments. In fact, I think that when RG blogged on their problems with Heroku, this is the style that they used.