Another thing I didn't talk about in my article was how to make sure your rich text edit controls are based on RichEdit 4.1 (which has TSF support). 

You need to do two things:

1)  change your window class name from RICHEDIT_CLASS to MSFTEDIT_CLASS, and

2)  LoadLibrary("msftedit.dll") instead of LoadLibrary("richedit.dll").

That's it!