I suppose it depends on with what one compares. Compared with Disqus, which is, according to the article, about 750 kb, then, light-weigth. Compared with Schnack, then not light-weight. So, maybe both "yes" and "no" makes sense.

Anyway it loads quickly on my mobile phone (before I've scrolled down to the blog comments if I start scrolling directly) — maybe that's what matters, anything else people aren't going to notice anyway. ... Hmm unless they're on a slow 3G connection, then would be good if I could remove more js.