Ok, having read this comment again, here's a more measured response. You're assuming in this comment the value-type vs. object-type dichotomy that's used in, e.g., C#. That's one way to go, but I'm not sold that it's the best way. Deciding whether you want something to be storable inline in arrays or not when you define a type is kind of a strange thing. Maybe sometimes you do and sometimes you don't. So the bigger question is really if that's the best way to go about the matter.

It seems that in dynamically typed languages, you either need to have two kinds of objects (value types vs. object types), or two kinds of storage slots (e.g. arrays that hold values inline vs. arrays that hold references to heap-allocated values). The boxing aspect is really only part of that since you can't get the shared-reference behavior unless the storage is heap-allocated, regardless of whether there's a box header or not.

So yeah, it's a complicated issue.