I think this is the critical point. The marginal utility is quite clear though: Readers can check all sorts of claims for themselves by looking up public details about the person. E.g. are they really a psychiatrist working at X as the reporter claims.
In the specific case though, given a really well established pseudonymous online identity, that is the central subject of the article, the marginal utility of the additional information you can check seems uniquely low. At least if the subject is just the pseudonymous activity of the author.
Maybe there's some case to publish his name if he's misrepresenting himself. It doesn't seem like that's the case. If the journalist finds discrepancies he can report on them too.
In the specific case though, given a really well established pseudonymous online identity, that is the central subject of the article, the marginal utility of the additional information you can check seems uniquely low. At least if the subject is just the pseudonymous activity of the author.