When using COM pointers, MSVC emits pretty long mangled names.
Example:
?_Release@?$_com_ptr_t@V?$_com_IIID@UIPiggyback@@$1?IID_IPiggyback@@3U_GUID@@B@@@@AAEXXZ
per http://demangler.com/ results in
struct _GUID const _IPiggyback::_com_ptr_t::_Release
Objdiff fails to demangle these and leaves them as-is.