Minidenticons are complex to manage at UI level, they clutter up the profile, imo.

WoT (first) + pet names are a good enough solution.

Another quite easy solution is to add an index (it could also be a component of the WoT, nostr:npub1jlrs53pkdfjnts29kveljul2sm0actt6n8dxrrzqcersttvcuv3qdjynqn?) that counts previous interactions (replies , reactions, zap) that you actively had with an user. This prove immediately that you are facing the real one.