If we can come up with a better tag, I'm all for it. I originally created system to cover low-level sorts of questions. Contexts and symbol naming, the kernel parser, evaluator, assignment etc...
Andy's [core-langauge] is one possibility, although that implies syntax to me for some reason.
How about [core-kernel]?
(I'm also not sure whether we need symbol. For the most part I think we're shying away from individual functions, although I expect there will be exceptions for things like
I have a third alternative: system-core. It doesn't imply syntax, and highlights that we mean the core components of mma.