It is a task for DT members as they can actually make people think twice before throwing false accusations.
We cannot make anybody do anything.
We are limited by the workings of the trust system.
That's why I'm asking a DT member to tag this user appropriately
That would be highly inappropriate and would most likely lead to that DT member being kicked off DT.
The only appropriate thing a DT member could do, would be to include Lucius in their trust list with a "~".
Which would basically render his feedback invisible.
There's no real need for this, though, because it is already invisible.
Also, the prudent thing for you to do is considered to be
talking with Lucius.
I.e. "why did you leave negative feedback?".