I think it would be great if the users of the forum themselves put a "plus" for a good message
That's what merit system is for actually but others would have to give you a +merit in order to gain one. You can see it on everyone's post in the upper right. If you want to give someone merits for a good message, then click it.
this system is good, but have to be modified. if i say i post quality posts but who knows who will give Mertis, we can not beg on that. thats biggest weakness.
sometimes we will stay member forever. but here bitcointalk alternatives will be born rapidly and move away
Of course merit cannot be begged. IMO the system is good as it is now and doesn't need modification. One will only stay as a member forever if the user does not do helpful posts.