Here's what the article list component implementation looks like:

import React, { Component } from 'react';

export default class ArticleList extends Component {
  render() {
    // The properties include things that are passed in
    // from the feature component. This includes the list
    // of articles to render, and the two event handlers
    // that change state of the feature component.
    const { articles, onClickToggle, onClickRemove } = this.props;

    return (
      <ul>
        {articles.map(article => (
          <li key={article.id}>
            {/* The "onClickToggle()" callback changes
                the state of the "MyFeature" component. */}
            <a
              href={`#${article.id}`}
              title="Toggle Summary"
              onClick={onClickToggle.bind(null, article.id)}
            >
              {article.title}
            </a>
            &nbsp;
            {/* The "onClickRemove()" callback changes
                the state of the "MyFeature" component. */}
            <a
              href={`#${article.id}`}
              title="Remove"
              onClick={onClickRemove.bind(null, article.id)}
            >
              ✗
            </a>
            <p style={{ display: article.display }}>
              {article.summary}
            </p>
          </li>
        ))}
      </ul>
    );
  }
}

You're just taking the relevant JSX out of the monolithic component and putting it here. Now let's see what the feature component JSX looks like:

render() {
  const { articles, title, summary } = this.data.toJS();

  return (
    <section>
      <header>
        <h1>Articles</h1>
        <input
          placeholder="Title"
          value={title}
          onChange={this.onChangeTitle}
        />
        <input
          placeholder="Summary"
          value={summary}
          onChange={this.onChangeSummary}
        />
        <button onClick={this.onClickAdd}>Add</button>
      </header>

      {/* Now the list of articles is rendered by the
           "ArticleList" component. This component can
           now be used in several other components. */}
      <ArticleList
        articles={articles}
        onClickToggle={this.onClickToggle}
        onClickRemove={this.onClickRemove}
      />
    </section>
  );
} 

The list of articles is now rendered by the <ArticleList> component. The list of articles to render is passed to this component as a property as well as two of the event handlers.