> My own critique of Scala is, I believe, well informed;

Sorry, but no it isn't and it's painfully clear to a lot of people.

> the fact that you consider its lack of minute detail as lack of evidence demonstrates the Scala's community obsession for tiny details to the detriment of a grander vision.

You have a lot of talent in interpreting things the way you want. If people would have said “there are minor inconsistencies, but Scala has a grand vision it focuses on and that's what counts” you would have turned around and argued that it's the lack of attention to detail which makes everything in Scala horrible.

Sorry, but I have seen how you do this more than I care to count already. It gets tiring and embarrassing to read.

People have tried to tell you that “making up facts to retroactively fit your opinions” is not a good thing and then you just do it again:

> I do not dispute that Scala's features are well integrated in the compiler.

Let's just ignore the way you try to derail the debate here and move the goalposts around for a minute, because probably everyone who has spent 5 minutes to look at the actual source code realizes how mind-boggling wrong this claim is.

The compiler goes to great lengths to catch all the weird corner cases and shield it's users from inconsistencies which e. g. sometimes arise when running on a JVM or having to deal with other languages running on that platform.

Please have a look at javac, fsharpc and others. None of them come even close to effort scalac does to present its users with a consistent, coherent behaviour. They just let the user deal with all those minor annoyances.

> Scala never gives a compelling reason why it is so useful to mix different concepts in a single language and pay such a heavy price in complexity, other than "sometimes it's better to use one and sometimes another". That's not a hallmark of great design.

Sorry, you mentioned it yourself already that your mainly interested in a language which dresses up Java's minor pain points. I can understand that when coming from that point of view trying to understand the reason why Scala does things in a certain way is not interesting. But you should at least differentiate between “there is no reason” and “I didn't care enough to look for the reason”.

> What big software development problem (as opposed to a PL research problem) does Scala solve?

- Abstraction and code maintenance: In all languages, you can arrive at a certain point where refactoring/abstracting things any further (to increase readability, maintainability, modularity) doesn't add more value than it costs. The difference is that in Scala you are the one who can make this decision, not the compiler. This is a huge advantage, which can't be understated, but is also hard to describe if you haven't seen it yourself. Dropping into an unknown code base and being able to be positive that changing/fixing/modifying one item involves touching one place, instead of possibly dozens or hundreds of pieces of code, is a considerable benefit.
(Not really related to this, but implicit classes are an interesting example of how lots of code maintenance issues are made impossible by design, when compared to inferior approaches like extension methods.)

- Long-term evolution and extensibility: Scala gives you lots of options and tools to evolve your code in a way which minimizes the impact on the consumers of your code. Have a look at how Scala doesn't expose any public fields in classes, how easy ensuring binary compatibility is with tools like the Migration Manager, have a look how typeclasses enable you to design your code with extension points in mind right from the start, have a look how @deprecated and friends allow you to have meaningful transitions between old and new code if necessary. This reduces the amount of technical debt accumulated over a period of time and makes it easy to keep existing code bases up to the changing/growing requirements of the real world.

- Closing the decade-old gap between data inside and data outside of a language: Type providers go a huge step toward a state where developers can just stop worrying whether their data is in the source code of their language, inside a database, stored in an XML file, or wherever else. This will be a huge productivity boost to all developers.