What happened to the "mutable struct" debate?

[Rezaei, Mohammad A.]

I recently joined the list and I can't find any references to the justification behind restricting value types to final fields (aka immutable).
As Brian says (http://mail.openjdk.java.net/pipermail/valhalla-dev/2015-January/000734.html), "There are some people who would prefer something more like mutable structs" and yet, the value types proposal (http://cr.openjdk.java.net/~jrose/values/values-0.html) takes immutability as a given.

Is the issue considered settled? Is the justification documented?

Thanks
Moh