Firstly, good on you for trying to promote the idea of a healthy use of the feedback/trust system.

My main issue with this is that you completely ignore the "Neutral" rating; which is terribly overlooked IMO. If it is your intention to enlighten others on the use of the system, perhaps promote the 3rd option. I personally see Neutral as a tool for notes on the account/users behavior whether positive or negative, but not a scam/trade dispute. In this category I would include #'s 3,4 from your positive column and #'s 6,8,13,14 from the Negative Column.

#5 from the positive column doesn't necessarily warrant trust, but they should be included in your custom trust list, or could be left as a neutral to "vouch" for the user.

#8 from the negative pile, could again be a neutral rating, because I'm assuming they completed the trade. What this comes down to is members leaving appropriate ratings in their references to signify it was a small trade, or by only leaving them neutral in the first place until.

Then on top of it just remind people that they are free to leave trust as they see fit, but should be willing/able to justify them, and that these are just some guidelines as you've interpreted them. This is just my opinion and how I try to apply the system.

Edit: sorry forgot to explain my reasoning on #6 in the negative column - Everyone has to start somewhere, I'm sure I know the case you are thinking of, and while it was a poor idea from the onset a neutral could have served just fine. Would someone deserve a Neg for trying to build a reputation as an escrow by starting out small?