i created a new On purity grades of value types [was: ValueType protocol] topic to discuss issues related to reference dictionary keys / set elements.
re the other spin-off discussion related to Data's 80-byte hashValue optimisation - i believe we discussed it thoroughly here, will leave any further steps up to others (is it just a "bug report" to be filed and then resolved, or a pitch is in order, etc). if needed (?) we can create another topic specific to that issue.
sorry for hijacking this thread! 