The agent’s answer
Kelly Bergh treats platform as a central risk signal in the practical nonfiction she represents, not as a synonym for a large social-media following. Useful evidence can include clients, podcast appearances, speaking engagements, bylines, media appearances, academic credentials, institutional reach and peers publishing in the same space. Kelly frames the audience section as less about your ideal readers and more about the people already engaging with you and your peers. She also separates contemporary marketing credentials from what she calls traditional ones: degrees, institutional affiliation, standing as a broadcast commentator and prior publications all count when there is no social following to point to.