A negative rating right now is completely useless and will be disregarded by the supermajority of the users (the same way that neutral ratings always have been). I'd actually advise against leaving them to save yourself the time and trouble; just skip straight into scammer flags.
That's unfortunate then. It still shows up right there on any board that displays it, just as visible. The only change there is that there isn't a trust score which I felt was less informative than a tally of all feedback left. I do think I'll still be leaving a healthy mix of them all, just going to be a while figuring out when to use what. I still like the idea of using the negatives because there is no guarantee that they'll be activated in a timely fashion, so it's a good back up.
I don't see any reason why people will outright ignore negative ratings. They will still review the ratings, and take them into consideration, but if there is no clear articulation as to why or how they are unsafe to trade with, they will be rightfully ignored.
I don't think it will be possible to weaponize the trust system anymore. Or at least it will be much more difficult to do so.