The scss namespace

The rules of the core under @stylistic/scss/<rule>, for stylesheets written in SCSS and parsed with postcss-scss. The recommended preset sets them under these names over **/*.scss and names no package, so a stylesheet is read by these rules as soon as the project tells Stylelint to parse its SCSS files as SCSS — which is what Your own syntaxes shows. A project that names no syntax has its .scss files read as CSS by the @stylistic/ names, and nothing warns it about that.

Every rule of the core is here, with the same options and the same documentation, and plain CSS is read exactly as the core reads it — a plain block of an HTML page beside a lang="scss" one included, so a mixed page is configured with these rules alone. What the namespace reads beyond the core:

• the constructs only Sass spells — placeholder selectors (%a), nested properties (font: { family: x }), @content and a reading through a module (ns.$a, ns.f()) — are passed over the way the core passes over what is not standard CSS, rather than misread as code; a variable ($a: b) with its map or list, and an interpolation (#{…}), the core passes over as well, since a plugin spells both over plain CSS;
• an inline comment (//) is a comment of the file: positions are counted and fixes written in the file as it is spelled, and no fix writes into such a comment;
• function-whitespace-after under never leaves the whitespace in front of a + or a - standing behind a call, since Sass reads such a sign as an operator (see the rule's README);
• the value-slash-space-* and media-feature-slash-space-* rules pass over a solidus Sass divides at — one beside a variable or a call of Sass's own, as in 4/$a and fn()/2 — and read every other solidus as the core does, var(--x)/2 among them.

This namespace is about the stylistic side of the CSS an SCSS file holds. The SCSS constructs themselves — @if/@else, @mixin/@include, variables, placeholders, // comments — have stylistic rules of their own in stylelint-scss, which reads the same files beside this namespace.