Why waste time clicking individual posts, if you can Ignore everything from that user with one click?
Because that won't affect their earnings, and hitting them in the wallet is the best way to get them to stop posting rubbish. (Which will make the forum better for
everyone.)
and negative trust could be used as a tool to combat abusers?
This would not be a good use of the trust system.
Obviously, I'm not suggesting that people should be encouraged to tag each other over isolated cases of what they consider incorrect use. I'm saying that the possibility of receiving (justifiable) negative trust from a DT member would make a fine hedge against anyone seriously considering engaging (either alone, or as part of a group) in a pattern of repeated abuse.