Earlier quoted context omitted.
That sounds like the same basic idea -- moderators putting a mark on posts that basically says, "An upvote for this is a negative contribution to the community." Is the problem with the general idea, or with one specific detail which could be modified in implementation (banning versus ignoring votes)?
The entire idea is problematic, massively , in that it allows for covert manipulation of a community. Why are a small handful of unaccountable people determining what is a "negative contribution", on the sly no less, when the whole reason for the existence of karma systems is to do that organically and by consensus? More importantly, what does such a system accomplish via deception that flattening such posts in a vis…
Easy example: Let's say there are 10000 people who like cat pictures and 150 people who like long, in-depth articles. I'm one of the people who likes long, in-depth articles, so I make a forum for people to post and discuss long, in-depth articles. 10% of the cat-picture-lovers happen upon my forum and are delighted to see a new place that they can post cat pictures. My 149 friends and I downvote these cat pictures with all our hearts, but we simply can't outvote the 1000 cat-picture-lovers. Even worse, a cat-picture-lover can look at and upvote a hundred cat pictures in the time it takes me to read one long-form article, so the content that the forum is intended for is buried before even the 150 long-content-lovers get to see it. So the complete destruction of my long-article forum happens organically and by consensus, just like karma systems are supposed to work -- but it's not a desirable outcome!
Basically, karma systems are good at finding something that some group of people will like, but if that's all you want, subreddits are a bad idea, because the entire point of them is to focus on a particular thing and exclude other things that very likely more people would like to see.
Like I said, all the true* subreddits show that there are people who want to have more focused subreddits. The idea that focus should be impossible if a sufficient number of people who are don't have that focus stumble upon the subreddit just doesn't seem very reasonable to me.