From what I observe merit is just a way of applauding or publicly appreciating user for a quality thread or comment that meets a demand or a need. The merit is a growth factor that's comes through our comments and posts . And Yes our growth in ranks depends on it but not our growth in knowledge we acquire from the forum about crypto.
Your observation is not wrong. Constructive and quality interactions with this community are appreciated by merits and this system was introduced to give spammers and useless posters a hard time to rank up and to enjoy privileges like reorganization in this community and slot in signature campaign.For you to get merit you to study what you about to discuss on,the topic you are about to reply or contribute to you have to study it and understand what it all about before getting to write on them.
It got no differences from writing constructive posts 
. But, being a good poster alone not enough but you need to be a good contributor to this community in some unique way.