-snip- Beg for merit might be the reason someone has get a negative trust -snip-
I think negative trust is not for cases like begging merit or pure spam but intended for fraud cases in trading so that other members can be more vigilant when they want to trade with that member.
-snip-
Use-case #1 is the old trust system, but I made the descriptions on the rating types a bit more general and removed the concept of a trust score. The numbers are now "distinct positive raters / distinct neutral raters / distinct negative raters". You should give these ratings for anything which you think would impact someone's willingness to trade with the person, but you should not use trust ratings to attack a person's opinions or otherwise talk about things which would not be relevant to reasonable prospective traders.
-snip- I don't agree with using the trust system for pure spam; that's not what it was designed for.