<div class="section section--info">
    <h2 class="section__header"></h2>
</div>

AND

.section {
    display: block;
}
    .section__header {
        font-size: 12em;
    }
.section--info {
    background: color: purple;
}

or

<div class="section section--info">
    <h2 class="section__header section__header--info"></h2>
</div>

.section {
    display: block;
}
    .section__header {
        font-size: 12em;
    }
.section--info {
    background: color: purple;
}
    .section__header--info {
        color: red;
    }

Does every MODIFIER need to exist for each ELEMENT inside of the BLOCK?