Ask HN: When should an open-source library stop supporting legacy browsers?

You can also rephrase the question as:

- Are you assuming full ES5 support when building libraries?

- Are you assuming partial ES6 support when building libraries?

- Are you pushing shim responsibility to the user?

- Are you ignoring browsers that are 1% or lower in market share?

- When should a library stop hand-holding older systems?

What's your opinion? When should a library shed off legacy browser code?

(legacy = IE10 and below, browsers older than the previous version)