Bad choice or no, the language is appropriate... Constants should remain constant at runtime. Variables should be allowed to vary.
I don't see why people think immutable strings is a good idea, for example. How do you ever build a text editor, if the strings can't be edited?
The language and notation is inconsistent with hundreds of years of use in maths and confusing for kids learning both maths and programming (at least it confused me).
Regarding your skeptism of immutable data structures, it's best to think of immutable data and data structures as copy-on-write instead of update-in-place. This is a technique that is currently very underused, for example most programming languages do not come with "persistent" copy-on-write collections.
I tried diving into the source code, and immediately ran into something new :: everywhere and starting googling....
Namespaces?!? - Looks like a solution in search of a problem.
The whole point of object oriented programming was to prevent reaching inside of objects from the outside, thus making then implementation independent from use... Namespaces seem to break that. Like leaving the cover off a machine so that you can push on one of the relay contacts by hand.
C, C#, C++ feel to me like Greek all sorts of keywords that make no sense, and random !@#$%^&*():"<>?[] everywhere
Somewhere at the top of all that code, there has to at least be one actual pointer variable where you keep track of the last revision, isn't there?
