Isn’t that purely interface-equality related “issue”? With Maybe’s you’d compare Maybe(interface(Maybe(T))) with T or with Maybe(T) and it would either non-compile or be a broken comparison again, depending on == semantics. Then we’d read on muddy == semantics which is broken or disallowing for easy comparison through an optional interface and forces one to build ugly ladders of pattern matching in otherwise one-liner lambdas.