Has there ever been an explanation to the logic behind using "sage" exclusively in the URL field and being able to exclude oneself from a public ID code simply by filling out the URL field (with "sage" or otherwise)? One aspect I can find (possibly related to Japanese culture) is that if someone wanted to sage a thread in a negative way, they would prefer doing it under complete anonymity, so they wouldn't use the URL field for any intended purposes anyway. I don't quite see how this carries over onto Western boards though.

Any ideas?