I had to set the setting in the admin page for the LDAP authentication to: Object class : inetOrgPerson (Im using rfc2307bis) LDAP schema.
Hope saves someone some time.
In fact, it was as "broken" as it's now. I mean, there was a bug that whenever you chose rfc2037 or rfc2307bis, Moodle internally selected the default values for everthing (instead of the rfc2307 specific ones).
Once we fixed it, we've discovered a new bug: that the values we specify for rfc2307 (and rfc2307bis) not always work. We are currently using posixAccount for the objectClass attribute, and that seems to work for severay people. But then there are people like you that need inetOrgPerson instead, and thus it doesn't work.
I'm not really sure what's the best way to fix it without breaking a lot of people's setup (providing it isn't broken in the first place).