I don't agree with your suggestion. Don't make my opinion too harsh or negative because we have our own opinions.
First, see how many admins do we have in this forum and with this number of users and the number of posts everyday they will not gonna do it. They will not check every thread every day and see if there is a merit-eligible post in that thread.
Second, I like the sMerit system because we can share our merits to everyone and at the same time we help them to rank up too. Yes there might be some users who are abusing it but as far as I know, there are some users here hunting the merit abusers and the admins punish them thru temporary ban or permanent ban.
When I first see this merit system, to be honest I said "What the f*** is this?" and I read theymos' post about the merit and I said again that "It will be harder for me to rank up". Several weeks later since the merit system has been added, I saw the benefits of this thru the meta thread. Many users were banned because of shitposting. Many shitposters probably left the forum and we don't care about them, we are just users of this forum. There are some users who abuse merit system and given a negative trust.
For me, I don't think that merit system needs to be tweaked or changed. I like how it is now.
P.S. I hope threads regarding merit will be stopped in the next weeks of the next months because its flooding the Meta Section.