Standard rules shows as error when they configured to be warning

'custom' severity highlighting doesn't currently work for eslint/standard - youtrack.jetbrains.com/issue/WEB-25697

Highlighting used for ESLint/Standard depends on severity defined in eslint configiration: severity 1 is highlighted as warning, 2 - as error

So, how do I change severity?

The only way is changing rules severities in eslint config. As standard rules can't be configured (https://standardjs.com/index.html#i-disagree-with-rule-x-can-you-change-it), using ESLint is your only option. You can make sure that all rules in your configuration have severity 1 - Webstorm will show them as warnings then

Got it, thanks.