If a user is in a group that has a Never permission for Can post without approval for some or all forums and that same user has any moderator permission, the approval check is by-passed. However, when running the Forum-based permissions mask on that user, it indicates that the value for Can post without approval is Never.

There may be some other permissions that are affected in the same way, but if a restrictive permission is overridden when a user has a moderator (or admin, probably, not tested) permission, the mask output should reflect that.