I think it is somewhere documented but just to make sure everybody is aware of it:
Do never use a certifier for organizational unit or organization for Quickr (Domino) users (also valid if using LDAP!) which is named "/QP". "/QP" is used internally by Quickr and you will get into trouble in this case. E.g. if you will register a place with the command "qptool register -install" all directory users with such a certifier will no longer be able to access their places as they will be converted to local place users.
You will need to manually correct all these users by using "qptool changehierarchy" after each register command.
I am quite sure there might be other problems as well so the best would be not to use such a certifier at all.