You wouldn't find the definition of a DT member anywhere on Google, but to give you an idea, default trust members are users who are, by default, trusted by community members and don't have any ill-intention towards their co-members in a given community. Mainly, these people have done something good for the whole of the community that's why they're given such trust. And as I can see, the Pharmacist only leaves negative feedback on those who are scammers, shitposting and spreading FUD most of the time. You can PM him about it, though I doubt he'll reconsider your request unless he sees change.