Internal elements overlapping <Section>

Question

The tag <b> superimposes the tag <section> see example when using padding:

Note in the image above that the light gray bar refers to section gets smaller height than the tag b. That is, the internal tag overlaps.

Also when I resize the browser to tag b overlap itself, without giving due spacing. See in the example below:

HTML

<section class="compartilhar">
<span>Compartilhar:</span>
<span>Compartilhar:</span>
<span>Compartilhar:</span>
<span>Compartilhar:</span>
<span>Compartilhar:</span>
<span>Compartilhar:</span>
</section>

CSS

section.compartilhar{
  width: 100%;
  max-width: 1200px;
  margin: auto;
  padding: 10px;
  box-sizing: border-box;
  background-color: #ccc;
}

section.compartilhar span{
  background-color: #333;
  padding: 15px;
  box-sizing: border-box
  font-size: 18px;
}

Answer 1

As already said, the tag b, is intended for text formatting and must be handled by means of a container, for example...

section.compartilhar{
  width: 100%;
  max-width: 1200px;
  margin: auto;
  padding: 10px;
  box-sizing: border-box;
  background-color: #ccc;
  display: flex;
  height: 100%;
  flex-wrap: wrap;
}

section.compartilhar div{
  background-color: #333;
  padding: 15px;
  //box-sizing: border-box
  font-size: 18px;
}

<section class="compartilhar">
<div><b>Compartilhar:</b></div>
<div><b>Compartilhar:</b></div>
<div><b>Compartilhar:</b></div>
<div><b>Compartilhar:</b></div>
<div><b>Compartilhar:</b></div>
<div><b>Compartilhar:</b></div>
</section>