I'm a chip designer and this article kinda cracked me up. For microwave signals on submicron lines, losses get very significant. It seems that PCB design inherits our practices in places these issues aren't so critical.

But then I wonder about applications. If you ignore this rule of thumb, and gang a few hundred boards together sharing a clock... will your signal survive?

Sometimes a 'superstition' is just common sense regarding edge cases - walking under a ladder won't have cosmic effects, but a dropped bucket of paint can leave a mark