While this prototype did not consider much, most applications on Ethereum do provide high levels of interoperability. An organization (or DAO) could write their own implementation for how their domain uses the endorse function on a contract, then have their members endorse information, which results in the organization endorsement (ex. endorsed by who.int) showing up when requirements are met, etc. A high profile person, like Elon Musk, could also sign stuff to have his signature show up on a reference. (ex. ElonMusk.eth endorses this reference as accurately representing the truth)
I think with this specific use case, the purpose is not as clear because endorsements on social media are already trusted by users. For users, even if this was correctly decentralized through a blockchain domain, it still would likely require developer interpretation for them to understand if the decentralized service is operating as expected.