I think it may be too strict currently. Try such change in code, to be able to insert the same HTML as in post editor.
Go to rife\advance\inc\customizer\sanitization.php lin ~105 and change this return wp_kses_data( balanceTags( $value, true ) ); to return wp_kses_post( balanceTags( $value, true ) );
I will think about adding the same change for next update.
Comments
I have just tested it, and changing the icon and HTML worked fine for me.
However, HTML that you can use here is limited to this list https://codex.wordpress.org/Function_Reference/wp_kses#Allowed_HTML_Tags_Array due to security. I will update documentation with this info.
So you may not be able to do some rich formatting here, only simple info.
With kind regards.
Go to rife\advance\inc\customizer\sanitization.php lin ~105 and change this
return wp_kses_data( balanceTags( $value, true ) );
to
return wp_kses_post( balanceTags( $value, true ) );
I will think about adding the same change for next update.
With kind regards.