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.