I believe Bitcoin Talk is a good forum for merits. They have some excellent boards there, and if you make quality posts, and become a good member, then they award you with merits.
Yes, we need merits. But how to be with those who received merit in the distribution and for 100 days they did not get the merit, but have a rating: full member, etc?

law does not have retroactive force.

It isn't, that's true. But we can help in cleaning the forum from shitposters by reporting low quality posts. I guess there is some penalty for too much shitposting... so in time, number of those that didn't deserve their rank will decrease.