i don’t know if it can save you some work, i’ve tested some more:
* adding only one of First/Last name works
* In every case, if from wordpress administration “Edit user” i change the “display name publicly as” to the nick or last name of the user that doesn’t change inside buddypress
I don’t know if this is a desired behaviour or not, so just hoping to be useful
Didn’t fill firstname-lastname!! That was obvious but i needed your answer to find it out, thank you!!
Also, adding firstname/lastname from admin panel to existing users didn’t solve the problem, while creating new users with firtst/lastname gives the correct behaviour.
