SetProp?
Not so much any more, but it could be a sign that you forgot something.
Customizing the QueryInterface and GetIids methods.
Prevent winrt::implements from responding to it or reporting it.
Filling in some gaps.
std::map or std::unordered_map?
Fancy emplacement.
PAGE_NOACCESS and freeing it?
Nobody can access it, but it's still there.
Looking at the tools you have available.
Don't punish people for looking.
std::enable_shared_from_this
Playing around with the standard library.
Take a closer look at what you are overloading.