Despite common opinion it is possible to use refs inside of a functional React component...

CommentForm.js

const CommentForm = () => {
  let author, text;
  const submitForm = e => {
    e.preventDefault();
    console.log(author.value);
    console.log(text.value);
  };
  return (
    <form onSubmit={submitForm}>
      <input type="text" ref={node => author = node} placeholder="Name" />
      <input type="text" ref={node => text = node} placeholder="Comment" />
      <button type="submit">
        submit
      </button>
    </form>
  );
};

This totally works, as proven by the console.logs!