There is currently no such thing as a "demerit". I'm hoping that the positive merits alone will be fine. I could add demerits pretty easily later on if necessary, though.
It would have been a nice thing to add demerit system in the forum and to regulate undesirable merits of users but users will abuse it. Unless it will still control by MERIT SOURCES or you create or appoint another DEMERIT SOURCES to demerit any post that is not necessary or not worth of meriting. With that every user will be posting quality posts in the forum. Although what is quality post might be different from different demerit sources. Because they might see it from different perspective. I also suggest that if the 'demerit' should be adding, let there be DEMERIT SOURCES to that effect so that there should be check and balance in the meriting source and demeriting source and also there will be division of labor among the two organs in forum.
With all due respect, I disagree with you, implementing a demerit system will rather cause more problems and confusion than good, personally, I think we already have all that we need, and that is a merit system, why then do we still clamour for demerit system? Does anybody merit a post by mistake?, I believe not, in the sense where nobody merits a post by mistake, I believe we don't need a demerit system at all because it will only create alot of confusion and disagreement amongst us.
Imagine you find a post which after reading, you find it helpful and you decided to merit it, and a demerit source comes around and removes the merit, how would you feel? You probably would feel or see yourself as someone who don't truly know what a good post is.
Or imagine you spent your quality time to create a very educative post, and other members found your post worthy and decided to merit it, but a demerit source for some reason(s) didn't find your post helpful as much and went ahead to remove all the merits you were given, how do you think that would make you feel? Happy?, of course not, you probably would see that demerit source as an enemy of your progress and would start hating him or her.
And on the other hand, seeing a low quality post and not meriting it is already as good as demeriting the post, and if for any reason, you wish to take a step further, the report button is there, you can click it to report the post to the moderator.