Only when I found that the Sigil has removed all '& s h y ;' from one my file during 'Reformat HTML' - I realized what this menu item really concerns .

Maybe it is better to clarify or extend the text 'Entities to Preserve' to make it more informative and precision?
Thanks.
PS.
“& n b s p ;” ⇒ “& # 1 6 0 ;” even when in the ignore list.