The system is basically more of a community based type of thing. You might want to read through this in order to have some idea
1. LoyceV's Beginners guide to correct use of the Trust system
2. DefaultTrust changes (2019)
3. Trust flags

The feedback left on the user profile is mostly based on past deals, services, user's trustworthiness etc. and at times users include reference links too, that you can try to check out and verify if indeed the feedback is accurate or not. The trusted feedback you see on profile by default is from DT (default trust) members or members you might have also personally added on your trust list.