Twitter appears to give blue tick verification to dead users including celebrities Kobe Bryant, Chadwick Boseman and Chester Bennington

Twitter users who want a blue check mark are asked to pay at least $US8 a month. (Reuters: Dado Ruvic, file)

Elon Musk's revamp of Twitter's blue tick service has hit another hurdle after it emerged that several dead celebrities and other high-profile users appeared to have been signed up to the verification service.

One of Mr Musk's first moves when he bought Twitter last year was to announce that the platform's blue ticks — which verify a high-profile user's identity — would no longer be free.