I like the Constantipolitan hat, but I didn't earn it after posting an answer on meta (maybe I'll get it after this question?).
So, is it only for per-site metas, or should it work on meta.stackoverflow.com too?
I want that hat!
This is fixed now -- Constantipolitan is being correctly awarded on Stack Overflow.
The bug was caused by the fact that Meta Stack Overflow and Stack Overflow have somewhat of a special relationship, in that your MSO user id does not necessarily equal your SO user id (unlike other meta/parent sites).