Instance annotations are rather similar to dynamic properties with a pre-known expressive name, i.e. the client can deduce from the name what type the dynamic property has.
In OData-933 we added use of instance annotations to $filter. It seems consistent to support in $select (and $expand), but we don't have a use case.
Opening this issue to track the fact that we considered, and are open, to adding support to $select (and perhaps $expand) if we come up with some interesting use cases.
If supported, make sure we consider contextUrl, etc.