If that's a concern, Unicode `Default_Ignorable_Code_Point` property [1] represents a set of characters that are suitable for steganography because they can be

If that's a concern, Unicode `Default_Ignorable_Code_Point` property [1] represents a set of characters that are suitable for steganography because they can be more or less safely ignored without affecting semantics. (And most of them even do not affect visuals, like higher variation selectors.) [1] https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=[:Default_Ignorable_Code_Point=Yes https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=[...:]