> I don't think we actually need `->void`

Yes, agreed.

> Would it have looked any less cursed if it just read `defer { CoUninitialize(); };`?

It's subjective but personally I still hate it.

> Agreed that the simplest "fix" would be to just rename the macro to be all-caps.

Actually I think the bigger part of my suggestion is switching from an object-like macro to a function-like macro [1], which makes it all a bit less magical.

[1] https://stackoverflow.com/questions/36126687/function-like-m...