C/C++/ObjC preprocessor line (e.g. an unbalanced string quote or
unmatched paren) don't interact syntactically with stuff outside
the CPP line.
Comment about text properties amended.
;; assume that these text properties are used as described here.
;;
;; 'syntax-table
-;; Used to modify the syntax of some characters. Currently used to
-;; mark the "<" and ">" of angle bracket parens with paren syntax.
+;; Used to modify the syntax of some characters. It is used to
+;; mark the "<" and ">" of angle bracket parens with paren syntax, and
+;; to "hide" obtrusive characters in preprocessor lines.
;;
;; This property is used on single characters and is therefore
;; always treated as front and rear nonsticky (or start and end open