It's not like a regular like you do on facebook or other social media platforms.
At bitcointalk.org, high merit score means that you have high posts quality, it means that you comments are really worth for some people because you got honored for them.
I think that in the future there are going to be more requirements, but at the moment you need to have atleast X amount of merit to advance for the next rank, and that's a good idea, because it prevents shit posters from getting advanced for high ranks.
It's going to do a simple thing, high rank is going to have a direct connection with the quality post, you won't find Hero members posting comments with non-sense as it's common to see now.