Whenever Raymond does that, I want to know more, just out of spite. He once banned discussion of a internal DWM api, I think one that made transparent windows t

Whenever Raymond does that, I want to know more, just out of spite. He once banned discussion of a internal DWM api, I think one that made transparent windows tinted, and I learned a great deal trying to figure out what he was hiding. So, I wonder now, what are the exact criteria according to which MS documented APIs? Why would they want to keep these criteria secret?