Setup > Brands > Brand > Announcement.
I added Font Awesome CSS to items in my announcement. Example:
Previously was:
<h2Knowledge Base</h2>
And changed to:
<h2><i class='fa fa-book'> </i> Knowledge Base</h2>
The editor strips out the changes and only leaves the original.
If I make the changes in source, then save it, the announcement will look as intended, but if I go to edit the announcement again, it lost those changes.
I have to save the code to a text file and then edit and paste in, which I shouldn't need to.
(On a separate note, please update your Font Awesome CSS to include the newer icons).