When the User Properties Rule is configured to prevent the entire value of a user property, there is an issue when the selected attribute contains a separating special character such as an underscore or a hyphen.
For example: User_23
Both sides of the special character (the underscore in the above example) are checked separately against the password.
So using the above example, the follow password examples will be rejects as it sees either "user" or "23" as a part of the password:
There is currently no workaround available.
This has been identified as a defect and has been logged under VSTS108322.