You can only earn merit if you make constructive and helpful post in this forum, but still it depends on the member if they will give you merit even if you know that you made constructive post.
this is honest and blunt truth.
it does not only depend on someone making a constructive post but also if the members reading it are willing to award their sMerits.
Some people are just not lucky and others are very lucky.
Myself i am not very lucky