See:
https://bugzilla.wikimedia.org/show_bug.cgi?id=45255
https://gerrit.wikimedia.org/r/#/c/50305/
Just in case this is controversial, I thought I'd bring this topic up on
the list.
We currently send 404s for empty user pages, even for valid users. It would
be ideal to use user page urls as OpenID provider identity urls, but most
users never create their user pages. OpenID expects identity urls to be
200s, not 404s. I'd like us to send 200s rather than 404s for any valid
user's user pages, whether the page has content or not.
- Ryan