I had to re-register completely and re-upload an avatar. I tried the normal login procedure first, but it didn’t recognize my user name or my email address. I effectively had to start over again from scratch.
Considering that my old account was registered on the 30th of April 2019, that thus begs the question when exactly the corruption of the database ─ PostgreSQL, is it? ─ occurred, and whether the missing accounts had all been registered around and after April 2019. 
Yes. Thats what everyone has to do.
The point I was making above was about someone using a gravatar (social/linked) sign-up (registration) and thus why an avatar appeared (and matches).
Everyone has to re-register, no matter when the old account was created.
Okay, thanks for explaining. I didn’t know that. It was my impression so far that certain accounts had survived the crash and had been imported into the new database. 
That’s the handy thing with gravatars - you don’t actually need to do anything. Use the same email address with a supported site, and your avatar is automatically pulled in.
The Penguin Lives Again!
I know it won’t affect me as i was a new member anyway. But is there a protocol if some clever clogs tries to pinch someone’s username from the old form? I’m sure it’s bound to happen