If you don't grasp that DASH has fungibility issues, you are the idiot, not me...
Please read a book on economics.
You can easily see in the coin history that they have been mixed or not...
These discussions tend to get characterised by a myopic obsession with cypher technology and "visibility" that doesnt necessarily lead to the right solution. A bit like someone trying to improve the performance of a bus by turning it into a formula 1 car and then saying that capacity doesnt matter.
Please read a book on economics.
Ok, heres the deal.
If we examine purely the privacy dimension of money systems, everything falls into one of two categories - cash or credit. These are fundamental and important archetypes for monetary privacy because they are almost mirror images of each other:
A. Cash: *
[1] - works peer-to-peer
[2] - is independent from any individual or legal entity
[3] - manifests as tangible tokens in the public domain
[4] - is openly endorsed through public consensus (i.e. does not require backing)
[5] - is anonymous but not private
B. Credit:
[1] - does not work peer-to-peer
[2] - is synonymous with an individual or legal entity
[3] - manifests as private bookkeeping entries hidden from public view
[4] - is privately endorsed by a trusted third party (bank)
[5] - is private but not anonymous (by virtue of property [3])
*
Strictly speaking, cash means gold or other such base, unbacked medium but for the purpose of the analysis we can think of it as paper notes since they are conventionally used on a peer-to-peer basis.
If you are a monetary engineer who portends to invent a new monetary medium, the first place to start is with those two paradigms and to plant your flag firmly in one or the other. The reason for doing that is that - being mirror images - any cross-contamination of properties from one paradigm to the other will weaken the archetype and therefore form an inhibitor to adoption. As a secondary consequence it will also form an inhibitor to its speculative valuation.
For example, privacy (as distinct from anonymity) enhances the value of credit money but diminishes the value of cash since its the public manifestation of cash that forms the basis for entries in credit accounts.
The reason I bang on about this is that Dash is the only currency which unambiguously implements the cash archetype as a priority over everything else. Cryptonote does not and Bitcoin with sidechains does not. In fact Cryponote specifically implements the weakest combination of properties from both archetypes - an obscured blockchain (consistent with the credit paradigm) but no backer (consistent with the cash paradigm). Bitcoin on the other hand implements anonymity over privacy (consistent with cash) but then goes and ruins its fungibility by boiler-plating on a frankenstinien appendage from the credit-paradigm.
When we further examine why the bitcoin devs have done this, it gets even worse. Their reasoning is that they think Bitcoin should be the dominant global crypto-currency and should therefore support all technical requirements and markets. Well whether that turns out to be true or not, its not their job as engineers to decide that outcome - its the job of markets. Their job is to design a near-perfect monetary medium which does not conflict with known optimal design requirements.
