I've identified a situation, which may lead to users being unable to login properly to a Wordpress-MU site if registered from IPB3 (and of course IP.converged).
The problem occurs in 2 cases:
- if the username in IPB contains characters out of the ASCII charset.
- if the username in IPB contains uppercase characters while being registered in the IPB before converging.
This leads to multiple accounts being created on the Wordpress site with the same username and email address while trying to log in trough the converged application.
I have not found an option, to force IPB to create logins in lowercase-ascii-only charset which is very unfortunate.