BuddyPress.org

@djpaul this might interest you:

a. Login via facebook in to a buddypress site.
b. ‘The user activates the account’ a achievement gets unlocked.
c. Delete the facebook user
d. Again Login via facebook (same account) in to a buddypress site.
e. ‘The user activates the account’ a achievement gets unlocked.
f. But when we see inside that user profile page, there are two ‘The user activates the account’ achievements.

That means when we delete the user in buddypress, the respective achievement of the respective user does not gets deleted along with it.