I think it's easy and complicated at the same time , merits can be given to you by those users who have merits (sendable).
These are sMerits and these should be given under given amount of time or else it will expire.
If a user thinks that your posts are constructive and of good quality then he will give you merits. This system has proved to be great because lazy and unconstructive users used to post shitty posts to get higher rank.