From that link, there's a explanation for why the court in South Korea rolled back this change:

The Constitutional Court said, "The system does not seem to have been beneficial to the public. Despite the enforcement of the system, the number of illegal or malicious postings online has not decreased. Instead, users moved to foreign Websites and the system became discriminatory against domestic operators. It also prevented foreigners who didn’t have a resident registration number here from expressing their opinions online."

Yeah, I would have preferred a more principled reason, but what can you do.