Wow. I didn't expect a post about a little-used Windows API function to generate 30,000 page views. In any event, some folks still doubt the "IsTextUnicode()" explanation, so I'm putting up the test app that I used to validate my theory before I blogged it.
Just run the app, and enter a string into the edit control. As you type, the app repeatedly calls IsTextUnicode() and shows both the result (Unicode/not Unicode) and the flags that IsTextUnicode() returns to indicate which tests it used.
Updated:I had pasted in the relevant chunk of the app source code, but it appears this blog template chokes on 70-column preformatted text. If you really want it, drop me a line.