I had admitted that I also gave positive trust with someone else who helping or in any had transactions trade on me before but that was all about personal opinion. Regarding leaving negative trust on newbie members, don't hesitate to leave feedback if you have captured evidence or archive that you feel that the user is very risky to deal with. Selling, scam attempt, or any fraudulent activities should have negative feedback to give awareness to other users. You might also open a scam accusation thread so that DT members will help you.
But if that is all about spamming the forum, posting a malicious link, and copy-pasting from the article. That's the work of the MODs, you can simply report them to the MODs by hitting the button "Report to moderator".