Windows allows the any of the UTF-16 character set in passwords.
From Technet regarding password complexity - see last bullet point.
Password must meet complexity requirements
This security setting determines whether passwords must meet complexity requirements.
If this policy is enabled, passwords must meet the following minimum requirements when they are changed or created:
Not contain the user's entire Account Name or entire Full Name. The Account Name and Full Name are parsed for delimiters: commas, periods, dashes or hyphens, underscores, spaces, pound signs, and tabs. If any of these delimiters are found, the Account Name or Full Name are split and all sections are verified not to be included in the password. There is no check for any character or any three characters in succession.
Contain characters from three of the following five categories
- English uppercase characters (A through Z)
- English lowercase characters (a through z)
- Base 10 digits (0 through 9)
- Non-alphabetic characters (for example, !, $, #, %)
- A catch-all category of any Unicode character that does not fall under the previous four categories. This fifth category can be regionally specific.