I guess that once the merit system was introduced, lots of users' merit score was set to 1000 by default, I just don't get why. Probably, because they had already a high rank and it would not be good if they suddenly get lower?
If I remember correctly the sort of "reasoning" would be that it would be unfair for the people that have contributed since the early days. Though even the spammers themselves managed to take advantage of it, it's still a fair excuse in my opinion. What's important is that it's already implemented and the succeeding spammers after the merit system implementation would have a really hard time ranking up.