[emn13]

I think it's usually a sign of a poorly understood domain or a poorly modeled problem. It's not a good sign; it's not necessarily a bad sign; it's (at best) an admission of one's limitations.

Comments become useful when behavior is implicitly tricky. Ideally you'd make the "trickiness" tangible and expressible in-whatever-language you're in, but that's not always easy to do.