Problem with stripped code

I have classic problem with WP visual editor when I am using the “Highlight word”. After saving the page is <span> and </span> tags stripped from content :-( Same problem in widget area.

I think the solution could be shortcode [span]…[/span] or how can I correct this problem? Turno off visual editor is not solution because then I cannot see button “insert shortcode” in basic html editor.