I have changed and saved the 'About me' section, but cannot get the Autobiographer badge for both main and meta sites. I did it several times and waited several hours, but the badge does not appear. Might it be a bug?
Most (all?) badges are awarded as part of a daily batch script that runs, so you should not expect to see them until up to 24 hours after you've performed the action necessary to earn the badge.
Presumably this avoids repeating costly (performance-wise) queries more than necessary.
Likely the place to find more information if you're interested would be to search on the main meta: https://meta.stackexchange.com