In the template editor there is the option to update copy text using a rich text editor text box.
These are used in multiple locations where text can be updated.
This editor also provides the option to edit the HTML for the text using a html toolbar option.
When selected the html code for the text will be available for editing to provide more advanced editing options.
To save the changes YOU MUST unselect the code mode before the changes will be reflected in the editor.
If you do not go back to non-html editor mode the changes will not save and they also will not reflect in the editor.