I’ve had a similar issue in other CMS:es.
HTML elements with 0 child nodes including text node.
<i class="fas fa-tint"></i>
This is from font awesome.
When pasted and saved Squidex removes the element (probably because it is empty). But this is the way some elements work in HTML/CSS.
A work-around is to add a not breaking space like this:
<i class="fas fa-tint"> </i>
When saved Squidex converts the
<i> element to an
<em> … not so cool…
Is there a way to override this behavior?