being able to transfer HANDLEs across the 16/32-bit boundary notably for COM/OLE integration becomes a lot more painful

Microsoft says at https://learn.microsoft.com/en-us/windows/win32/winprog64/ru...:

> Note that 64-bit Windows does not support running 16-bit Windows-based applications. The primary reason is that handles have 32 significant bits on 64-bit Windows. Therefore, handles cannot be truncated and passed to 16-bit applications without loss of data. Attempts to launch 16-bit applications fail with the following error: ERROR_BAD_EXE_FORMAT.

winevdm on Windows eschews that level of integration, but perhaps MS should have shipped WoW16 with limitations instead of nothing.