At that point, why use the trust system at all.
Trust system haven't relation with posting quality, again spamming/shitposting exist simple, available to all "report to moderator" system.
Neutral feedback makes it hard to spot those users (eg think about a campaign with 100 users, a manager would have to parse 100 trust pages to spot such tags, as they dont show up like negative trust does).
The reason some use negative feedback to tag spammers/shitposters is because it stands out. It's easy to spot.
You're talking like the Forum should adapt trust system to signature campaign and help their manager. Why should this be? They work for a paid job.
(Note that I, currently, do not leave negative feedback for spamming/shitposting. My apprach to this prolem was initializing SMAS, if you want to contribute to that approach, feel free to contact me.)
This is welcome.