The advertiser, meaning whoever controls the site or review function, is responsible for testimonials in advertising: the clinic for its own website and business social media (reviews may need to be switched off where they cannot be edited), and the platform owner for third-party booking or review sites the clinic does not control. Patients remain free to post reviews on independent platforms and an advertiser need not chase removal of them, but engaging with reviews on a third-party site can itself use a testimonial.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.