In a world of imperfect information, how do you prove to a stranger that you are knowledgable, in less than a full day of interaction? That remains the problem

In a world of imperfect information, how do you prove to a stranger that you are knowledgable, in less than a full day of interaction? That remains the problem, and credentials/prestige remain our best way of dealing with it. In other fields you develop portfolios (e.g. github repos) perhaps that's what education will evolve to, developing a student work portfolio to prove you are knowledgable.