TYPO3 Core

demo-source:
<ul class="unstyled ul-app ul-check">
<li><span class="icon-check"></span> demo1</li>
<li><span class="icon-check"></span> demo2</li>
</ul>

The spans with icon-check get removed.

I've also already searched for solutions. Some target using allowedContent - but our "extraAllowedContent"-setting should already allow quite some things. Even filling the spans with something does not seem to protect them from being removed.

When editing a record with a RTE-field containing the above mentioned HTML it gets loaded fine in the frame - but gets removed by ckeditor upon loading. switching to the source-view (without saving) does not show those spans anymore. Saving then proves the spans are also removed in the frontend.

Switching to the source-view and saving it's possible to add the above mentioned HTML - but opening the record and saving it again removes the spans.