Interesting addition: I can indeed imagine leaving a positive feedback when an otherwise trusted member gets negative feedback for no good reason. But for other cases, I'd stick to neutral only.
"If you wouldn't give them a positive trust without the need for a counter, don't give it to them using the counter" seems like a good line of thinking.
I agree with this. If there is no need to give positive trust in the first place then there is no need to give positive counter-feedback trust. That rule seems simple enough for any and all members to follow.
It seems like a sizeable number of members in the forum are operating as they want by picking which parts of the trust system and other forum rules to implement and accept. Then some of those members do not accept it when other members implement their own interpretation of the very same rules. Having broad consensus between members (or at least those are DT) would have given a direction to follow since the trust system is not being implement correctly by too many members.
Some users would argue,
it's not a bug - it's a feature, in that the (relatively) free framework of the wide-scoped DT100 system results in a large pool of members participating in a coordinated effort to organically formulate a democratic-esque system of which to operate.
Others would say that the vastness of the space results in many interspersed leaks of abuse and corruption which can sometimes pool into a puddle of members. The interpretation of the trust system and its guidelines vary across users (e.g. account sales, bounty abuse) but consensus is never going to happen all at once - the pigeons need to be fed crumbs at a time before their stomachs become loaves.
Recently I completely overlooked exactly just how much of a well thought out writer you are... detailed with deep thinking and only elaborate where necessary. You could moonlight as an author in one capacity or another. My respect to you
actmyname 
It is often quite vague, the threshold of "bad feedback" that a particular user can send before they are distrusted, yet one way we can curb a factor that may prevent users from doing so is to continually post redundant feedback such that the DefaultTrust coalition (so to speak) does not have to rely on a single point of failure for displaying negative trust/flags against a large swathe of scammers or
worse* users.
* worse than the DT member, however marginal.
The threshold is effectively open to interpretation as much as it is open to abuse. I have seen a number of members that have pointed out feedback they find questionable by citing it inappropriate by virtue of the trust system guide but then they themselves do the same by leaving positive counter-feedback.
What I
do like about the trust system in general is that it effectively allows people to create policy-based (by way of representatives or themselves directly) bubbles of interaction in which users can choose the particular space they want to operate within. For any unconventional-trust users, they are allowed to distrust any relevant DT members and form their own DefaultTrust circle. You have seen this happen, you are seeing this happen, and you will continue to see this happen.
That's a good thing, though: reliance upon the base trust system is, of course, only a measure by default. I just wish there was an
accompanying guide for new members that join the forum.
What you mentioned about DT members forming their own DefaultTrust circle and that "
you have seen this happen, you are seeing this happen, and you will continue to see this happen", that assessment seems true and you make a valid point. I would further add to your comment by saying that there is no evidence of any DT members forming their own DefaultTrust circle via collusion with nefarious motives and that the default trust circles you refer to could have been created on more of a subliminal level rather than out-and-out skulduggery.