I really think DT system should be used to prevent people from scamming (or make it a little more difficult at least).
If we leave negative trust to shitposters I think people can end up ignoring the feedback left to scammers/untrustworthy users.
I disagree. The whole point of the feedback, even now, is that you read what it is about. Certain negative feedback can be safely ignored if you want to deal with someone.
Not likely if you're a Buyer/Seller. The Red Marking can easily discourage potential customer whom I think is too busy/lazy to read all the feedbacks.