Sorry, dumb question. Don't usernames have to be a certain amount of characters? Then how do people have 1 letter usernames?

You can create an account that has a 1 letter username. You can ISS to a name with 3 letters or more.

At the create account page I tried one letter usernames and they were all invalid.

Oh well. Doesn't matter for me if an ISS requires at least 3 letters.

It's possible that rule was changed then, it was once possible to have a one letter UN.

Sounds likely since quite a few user pages of single letter usernames appear completely blank (which I understand to mean there is no user with that username currently), but still appear as invalid in account creation.

You used to be able to create them, but cannot anymore