Yeah, I know there's an edit button, but at the time I really didn't feel like doing the editing required, since it wasn't just a matter of "should have added this" - to edit in the correction I would have had to change and rewrite significant chunks of the text, such as the summary, and it was already late (getting towards early), and it would have taken enough time that others might have read the first version in the meantime, so I'd have to add something about the correction anyway, and... yeah.
I suppose I could have added my reply as an "EDIT:" at the bottom or something, but it felt more appropriate as a reply, since it was a pretty significant correction. (And in my mind, double-posting is something entirely different than responding to yourself. But I guess I might be out of touch on that.)