React eslint not catching the use of underscore with internal methods

In the [React/JSX Styleguide 'Methods' section](https://github.com/airbnb/javascript/blob/master/react/README.md#methods) it says you shouldn't use `_` to prefix internal methods. However, some of my code contains this convention and it isn't being caught by the linter. I double-checked the eslint rules for react/jsx files and there doesn't seem to be a rule defined for this convention.

Is this intentional? If so, why specify the rule in your documentation? I found a related issue (#490), but it wasn't clearly stated whether or not this rule should definitely be adhered to but rather that it's more or less up to the programmer.

Any clarification would be greatly appreciated.

react/README.md の React/JSX Styleguide の「Methods」セクションから始め、React/JSX ファイル用の既存の ESLint ルールを調査してください。関連する issue #490 を確認し、文書化されているアンダースコア規約を適用すべきかどうかを判断してください。ポリシーを決定し、それに対応するドキュメントまたは linting の変更を行えば完了です。

索引モデルが issue の本文から書いたものです。