Personal Testimony as Evidence of God's Existence

A leading argument for God's existence is the design, or fine-tuning, argument. A less common one is from personal testimony. This purely subjective evidence carries emotional weight, but its validity is strictly limited and open to critique.
Conversion experience offers no objective veracity. A personal testimony demonstrates that a belief has changed a person's life, but it cannot prove that the underlying metaphysical claims are universally true. For example, deeply moving testimonies of radical moral transformation exist across religions as diverse as Christianity, Islam, and Buddhism, as well as secular movements. Because these belief systems mutually exclude one another, individual subjective experience cannot dictate objective truth.
Adding another layer to this discussion is social and narrative conformity. Sociological studies note that individuals often subconsciously reshape their life stories to align with the established "testimony lingo" or expectations of their religious community in order to gain social acceptance. Additionally, testimonies of famous prisoners are often ridiculed as weak attempts at forgiveness for horrendous crimes.
Despite these complications, do radical conversions do carry any weight? Does the empirical reality of visible change, such as sudden recovery from addiction or a radical shift from hatred to altruism, provide any evidence for the existence of God?