Proposal: Programming Language Design
The vast majority of the high-scoring questions at the moment are about the technical side of programming language design (how do I implement ...). Many of them will also work on CS.SE as pointed out by pxeger here. I don't think PLD.SE should limit itself like this, but also accept more "developer experience"-related questions, e.g. how a decision will impact developer productivity, or how to give better feedback to the programmer, etc.
Are non-ASCII operators a good idea, and why? - If this question is changed to asking about pros and cons, I think it is a perfectly fine question about developer experience. It certainly impacts how a programmer can effectively use the language. A good answer would include how hard it is to set up a custom input (keyboard layout, editor setting, or other tooling support) and how some Unicode chars are used for better expressiveness in various existing languages.
How can I show multiple parse errors at once? is more of a technical question, but also touches on the UX side. Producing good error messages is a critical part of a language's usability, and producing multiple errors at once is the first step forward.