I went and analyzed the 40 questions with score 10 and above that define the proposal, checking their suitability for Computer Science.
When creating a programming language, should I choose an LL or LR grammar?
Too broad as is. Squarely on-topic once edited to add information about the language.
What are the downsides of adding type inference of local variables? That is, does type inference preclude certain other features?
A bit broad. Squarely on-topic.
Is the Switch / Select Case structure worthwhile or can you get away with just If ... Else If?
Elementary, but on-topic.
Is it possible to make variable assignment a well-typed expression of a functional programming language?
I don't understand how the answer isn't trivially yes (maybe something got lost when shrinking the question down to a title), but anyway, this is dead on topic.
How to reduce the impact of garbage collection on runtime performance and responsiveness?
Too broad. A more specific question would be perfectly on-topic.
How is multimethod dispatch implemented?
A bit broad, but on-topic. (How it's implemented in a specific language might not be.)
What features of the grammar for a programming language make it easier to implement a REPL (command line interface)?
Too broad, but on-topic.
How does one guarantee that the commutative, associative and distributive Laws hold for a type?
Too broad, but on-topic.
Is there anything you can do with an eval() type function that would be impractical to implement in any other way?
We have it already.
Are there any good resources for the design of new languages available? (which features should (not) coexist, what fits for certain domains and so on)
A poster child for too broad, and not suitable for Stack Exchange. But topic-wise, no problem.
Should a drag-n-drop language (e.g. Scratch) actually be considered a programming language?
On-topic.
What are the advantages / disadvantages of indent and line break syntax (like Python) compared to curly brackets and semicolons (like C etc.)
Flame-prone, but if it can work anywhere, it's on a site with scientists who are used to backing up their assertions. Risks being too opinion-based, but on-topic.
What, if any, are the benefits of functional programming languages over imperative languages?
Too broad, but on-topic.
What limits are imposed by compilation-to-C? Does it render some language features impossible?
Rather broad, but on-topic.
Why does C++ disallow use of unused symbols as operators? (Such as @ or $...)
Borderline, as it's about a design decision for a concrete language. Can be made firmly on-topic by pushing towards the reasons why one would allow or disallow it.
What are the practical alternatives to conventional 'libraries' for packaging, sharing, and reusing code? Do any of them eliminate configuration hell?
Too broad, but on-topic.
What is being added to languages to ensure they produce provable code e.g. type inferencing, proof carrying code, models that can be verified, i.e. F*
Too broad, but on-topic.
What is a straightforward tool or process to help define a language grammar?
Too broad, but on-topic.
What is a memory-efficient way to implement dynamic array size?
Too broad, but on-topic.
To what extent do type safety and memory safety help or hinder programmer productivity and runtime performance?
That's more of a software engineering question than a computer science question. That being said, scientific analysis of software engineering is an existing, if slow to emerge, field. We're a bit waffling on these.
What properties makes a language good or bad for 'live coding' (i.e. programming as performance)?
On-topic, perhaps too broad.
Is type inference essential for typestate (e.g. in Mezzo or Plaid) to scale?
Firmly on-topic.
The C++ preprocessor is non-Turing-complete. How do languages with Turing-complete preprocessors (Scheme?) deal with unbounded compilation time?
On-topic.
Wolfram's new language is the first I've seen that integrates a massive knowledge base. What are the security implications of this design?
On-topic.
How can Hindley-Milner type checking be applied in the design of a new language?
Unclear what you're asking. But all the parts are on-topic.
Why do some languages use := for assignment and = for equality versus = for assignment and == for equality, and what are the advantages of either?
Syntax again, somewhere between science and history of technology. Borderline.
What is the smallest programming language (statements etc.) that not only is Turing-complete, but also useful for teaching programming to beginners?
Flame-prone. But if it can succeed anywhere, it needs to be asked in a venue for people who teach computer science. Here is where they hang out.
What features are necessary or useful for systems programming, especially embedded systems?
Too broad. Could be construed as a question for computer scientists or for programmers.
What's the easiest way to hook up a garbage collector to the object code generated by a new compiler?
Would need more information about that compiler. With that, on-topic.
What is the cleanest way to define a type that represents a process with multiple input/output streams? (parallel access, multiple possible errors)
The question needs clarifying: is it about language design (→ CS.SE) or about API design (→ SO)?
How can I go about implementing a language that allows concurrency?
Too broad, obviously. All the steps would be on-topic.
What features are essential for a PL to serve as a 'systems' language?
Duplicate of #28, which is too broad and borderline.
What are the known lexer+parser algorithms? Can an exhaustive list of all strategies be created how to transform textual source into AST?
Too broad, on-topic.
Futamura projection is difficult to implement. If we go for all-out speed or all-out size (tersity), does it become straightforward?
On-topic.
Is it possible to integrate Session Types into imperative language?
Requires a bit more information about the kind of imperative language. On-topic.
What are the real life programming constructs depending on dynamic typing that are so useful that they can justify using a dynamically typed language?
On-topic. Maybe too broad.
Are there any technical reasons why one language cannot be appropriate for systems/scientific/web scripting etc. usage?
Too broad. Could be ok if more focused, but would also be ok on Programmers.
Shouldn't product types be commutative? (Int * String = String * Int) just as sum types (Int + String = String + Int)
Definitely on-topic.
In a certain language, the relative position of each token fully defines its semantics. What are the brackets, commas and other punctuation for, then?
On-topic.
Where can I find a description of the algorithm for a functional language that checks that an algebraic type is fully covered by the match function?
On-topic.
I am a former academic in the field of programming language theory. I consider Computer Science perfectly adequate for questions in that field. I would find it harmful to split computer science into niche sites. Niche sites do make some sense for cross-disciplinary topics such as cryptography or machine learning, but for core computer science topics, there is no sense in forcing people into cells.
