JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<textarea id="answer"></textarea>
<hr>
<div>
    <span>Вася</span>
    <br>
    <p>Все прост!</p>
    <button>Ответить</button>
</div>

<hr>

<div>
    <span>Петя</span>
    <p>Как?</p>
    <button>Ответить</button>
</div>

<hr>

JavaScript

$('button').click(function(e){

	e.preventDefault();

	var 
  	field = $('#answer'),
  	fieldVal = field.val();
    
  var 
  	fullMessage = fieldVal + $(this).siblings('span:first').html() + ', \n';

  field.val(fullMessage);
});