Criteria 3.
Firstly, there is now a neutral rating type. Neutral ratings don't affect a person's trust score at all. On a person's trust page, positive ratings are bold, neutral ratings are italic, and negative ratings are red bold-italic.
Secondly, it is now possible to exclude users in your trust list. Prefix a person's name with a tilde character (~) if you want to exclude them. If you exclude someone, then you will never see that person's ratings as trusted, even if the person is trusted by other people in your trust network.
Exclusions also travel through the trust network. If one person in your trust network trusts someone and another person excludes them, then whether or not they're seen as trusted for you is decided using these rules:
1. If someone at a lower depth (ie, closer to your trust list) disagrees with someone at a higher depth, then the person at the lowest depth wins. Due to this, no one can overrule anything you put in your trust list directly.
2. If multiple people at the same depth disagree, then the rating type that is most popular among these people wins. For example, say that you have three people in your trust list. If two of them trust someone and one of them excludes that person, then the person will not be excluded.
3. If an equal number of people at the same depth include and exclude a person, then the person will be included.
Finally, I added an easier-to-understand way of viewing your trust network to the trust settings page. The number in parentheses is the number of people in the preceding (lower) depth level who trust the person minus the number of people at the preceding depth level who exclude that person. This view contains slightly less information than the hierarchical view -- there's a link to the old view at the bottom of the trust settings page.
Also, the maximum trust depth is now 4 instead of 3, though it's probably still not a good idea to go above 2.