I saw that user creation log and that does seem to me to be persuasive evidence, but persuasive evidence may not be conclusive proof. Carl Sagan said that "Extraordinary claims require extraordinary evidence https://en.wikipedia.org/wiki/Sagan_standard", and I understand if people would like evidence that is more verifiable to the public than a CU's testimony, especially keeping in mind that hoaxes have been a problem on English Wikipedia https://en.wikipedia.org/wiki/Wikipedia:List_of_hoaxes_on_Wikipedia. However, I also think that "assume good faith https://en.wikipedia.org/wiki/Wikipedia:Assume_good_faith" applies here, and I am mindful of another user who said that people made demands for proof of their authenticity in a way that sounded to me like the interrogators' primary motivation was harassment. Perhaps "Trust, but verify https://en.wikipedia.org/wiki/Trust,_but_verify" fits how I'm thinking about this. The currently available evidence wouldn't be enough for me to feel comfortable with sending out a press release, but internally (in Wikimedia spaces) I would be happy to celebrate good news if this person is able and willing to publicly associate the Wikipedia account with their identity as an astronaut.