I'd expect anyone experienced with C would say that making such casual, deliberate use of the underflow for such a trivial purpose is pretty foolish, the mark of a developer too clever for his own good. I thought the author was perhaps suggesting this with sarcasm: "Wizened sourcerers" and "full clever." But maybe not.

C's variable promotion system is invisible and silent and in my experience a frequent source of bugs in exactly this case (tests in for loops), which is why there's enough meat here for a blog post. It's usually easy to avoid the promotion issue by using the same type for the loop variable and its test condition. In cases like this, sometimes it's better to just use a straightforward and obvious while() loop instead of a correct but tortured for() loop. That makes the relationship between the loop variable updates and the loop body controllable and explicit.