5. You
can't rename a global account.
We'll definitely be wanting that in the long run. Need to be clear about
permissions, though...
What may be best for most cases is likely to allow people to rename
their own accounts cleanly. The simplest, from a user and anti-vandalism
point of view, would be to make it easy to link a new name to your
existing account; you could then go by the new name, but retain your
credentials, history, edit count etc while keeping the visible link to
the old name for public tracking purposes.
Something to consider, anyway.
It's more urgent to enable renaming *to* a global account. Everybody
started today noticing they have collisions and wanting to usurp for
different accounts.
However, once the global account is created there's no way to merge the
one with a different name as the CentralAuth renaming is not active.