Some users have suggested that a up vote could be introduced which would show that they appreciate the post but, don't think it's worth a merit. The only thing with Stack exchanges system it wouldn't likely work at this forum. Stackexchange is primary used for asking and answering questions. But, this forum is much more complicated than that, and there's probably no real incentive of having an alternate account on stackexchange where here there's multiple reasons why someone may have an alt.

This opens the possibility of abuse, but not only from alt accounts. A lot of people have made a lot of enemies around here specifically those who point out scams and would be targeted by these down votes. This is also why a lot of people including myself are against the idea of a demerit.

I think if we ever introduce a system like this it would have to be limited to a 'like' and you could like a post. Honestly though, I don't think it's a big priority and there's probably better things to worry about.