"'{0}' is declared but its value is never read.": {
        "category": "Error",
        "code": 6133,
        "reportsUnnecessary": true
Examples
Suppose someone is writing new code and not quite finished yet.
const x: number = 123;
const y: number = 321;
const product: number = x*y;
// TODO: Do something with "product"
They have not used x yet, but they certainly plan to use it when they are done writing their code.  When you run tsc the output looks like this:
src/index.ts:9:5 - error TS6133: 'x' is declared but its value is never read.
With a professional build orchestrator, this "compiler error" will:
be printed in bright red, distracting attention from legitimate errors (e.g. calling a function that is not defined)
prevent downstream dependency projects from building
possibly also prevent other tasks (e.g. Jest) from running for the current project (we don't run tests if the code doesn't compile)
Proposal: Make it a warning instead:
    "'{0}' is declared but its value is never read.": {
        "category": "Warning",
        "code": 6133,
        "reportsUnnecessary": true
Checklist
My suggestion meets these guidelines:
 This wouldn't be a breaking change in existing TypeScript/JavaScript code
 This wouldn't change the runtime behavior of existing JavaScript code
 This could be implemented without emitting different JS based on the types of the expressions
 This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
 This feature would agree with the rest of TypeScript's Design Goals.